I thought that Banshee was checking for the existence of a file before trying to tell GStreamer to open it, however today I just tried to do this with v.2.6.2 and it crashed pretty badly (unmanaged crash):

(Banshee:25593): GStreamer-CRITICAL **: 
Trying to dispose element playbin, but it is in PLAYING instead of the NULL state.
You need to explicitly set elements to the NULL state before
dropping the final reference, to allow them to clean up.
This problem may also be caused by a refcounting bug in the
application or some element.


(Banshee:25593): GLib-GObject-CRITICAL **: g_object_ref: assertion 'object->ref_count > 0' failed

(Banshee:25593): GLib-GObject-CRITICAL **: g_object_unref: assertion 'object->ref_count > 0' failed

(Banshee:25593): GStreamer-CRITICAL **: gst_object_unref: assertion 'object != NULL' failed

(Banshee:25593): GStreamer-WARNING **: Element 'uridecodebin29' is not in bin 'playbin'
GLib (gthread-posix.c): Unexpected error from C library during 'pthread_mutex_unlock': Invalid argument.  Aborting.
Stacktrace:


Native stacktrace:

[Error 19:04:40.292] GStreamer resource error: NotFound
[Error 19:04:40.293] GStreamer resource error: NotFound

(Banshee:25593): GStreamer-CRITICAL **: 
Trying to dispose element identity, but it is in PAUSED instead of the NULL state.
You need to explicitly set elements to the NULL state before
dropping the final reference, to allow them to clean up.
This problem may also be caused by a refcounting bug in the
application or some element.


(Banshee:25593): GStreamer-CRITICAL **: 
Trying to dispose element aconv, but it is in PAUSED instead of the NULL state.
You need to explicitly set elements to the NULL state before
dropping the final reference, to allow them to clean up.
This problem may also be caused by a refcounting bug in the
application or some element.


(Banshee:25593): GStreamer-CRITICAL **: 
Trying to dispose element aqueue, but it is in PAUSED instead of the NULL state.
You need to explicitly set elements to the NULL state before
dropping the final reference, to allow them to clean up.
This problem may also be caused by a refcounting bug in the
application or some element.


(Banshee:25593): GStreamer-CRITICAL **: 
Trying to dispose element abin, but it is in PAUSED instead of the NULL state.
You need to explicitly set elements to the NULL state before
dropping the final reference, to allow them to clean up.
This problem may also be caused by a refcounting bug in the
application or some element.


(Banshee:25593): GStreamer-CRITICAL **: 
Trying to dispose element audiotee, but it is in PAUSED instead of the NULL state.
You need to explicitly set elements to the NULL state before
dropping the final reference, to allow them to clean up.
This problem may also be caused by a refcounting bug in the
application or some element.


(Banshee:25593): GStreamer-CRITICAL **: 
Trying to dispose element streamsynchronizer23, but it is in PAUSED instead of the NULL state.
You need to explicitly set elements to the NULL state before
dropping the final reference, to allow them to clean up.
This problem may also be caused by a refcounting bug in the
application or some element.


(Banshee:25593): GStreamer-CRITICAL **: 
Trying to dispose element playsink, but it is in PAUSED instead of the NULL state.
You need to explicitly set elements to the NULL state before
dropping the final reference, to allow them to clean up.
This problem may also be caused by a refcounting bug in the
application or some element.

[Error 19:04:40.297] GStreamer resource error: NotFound
[Error 19:04:40.298] GStreamer resource error: NotFound
	banshee() [0x4b73d8]
	/lib/x86_64-linux-gnu/libpthread.so.0(+0x10340) [0x7f5781bc9340]
	/lib/x86_64-linux-gnu/libc.so.6(gsignal+0x39) [0x7f5781829f79]
	/lib/x86_64-linux-gnu/libc.so.6(abort+0x148) [0x7f578182d388]
	/lib/x86_64-linux-gnu/libglib-2.0.so.0(+0x1b453) [0x7f577e65f453]
	/lib/x86_64-linux-gnu/libglib-2.0.so.0(g_mutex_unlock+0x23) [0x7f577e6ce9d3]
	/usr/lib/x86_64-linux-gnu/gstreamer-1.0/libgstplayback.so(+0x1fad2) [0x7f5759705ad2]
	/usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0(+0x105e7) [0x7f577d2d15e7]
	/usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0(g_signal_emit_valist+0x438) [0x7f577d2ea088]
	/usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0(g_signal_emit+0x82) [0x7f577d2eace2]
	/usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0(+0x105e7) [0x7f577d2d15e7]
	/usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0(g_signal_emit_valist+0x438) [0x7f577d2ea088]
	/usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0(g_signal_emit+0x82) [0x7f577d2eace2]
	/usr/lib/x86_64-linux-gnu/gstreamer-1.0/libgstplayback.so(+0xe446) [0x7f57596f4446]
	/usr/lib/x86_64-linux-gnu/gstreamer-1.0/libgstplayback.so(+0x1098b) [0x7f57596f698b]
	/usr/lib/x86_64-linux-gnu/libgstreamer-1.0.so.0(+0x5ed2a) [0x7f5769f38d2a]
	/lib/x86_64-linux-gnu/libglib-2.0.so.0(g_hook_list_marshal+0x84) [0x7f577e67e0b4]
	/usr/lib/x86_64-linux-gnu/libgstreamer-1.0.so.0(+0x26e2a) [0x7f5769f00e2a]
	/usr/lib/x86_64-linux-gnu/libgstreamer-1.0.so.0(+0x5fd6b) [0x7f5769f39d6b]
	/usr/lib/x86_64-linux-gnu/libgstreamer-1.0.so.0(+0x60348) [0x7f5769f3a348]
	/usr/lib/x86_64-linux-gnu/libgstreamer-1.0.so.0(+0x5e632) [0x7f5769f38632]
	/usr/lib/x86_64-linux-gnu/libgstreamer-1.0.so.0(gst_pad_push_event+0x378) [0x7f5769f42618]
	/usr/lib/x86_64-linux-gnu/libgstreamer-1.0.so.0(+0x6879f) [0x7f5769f4279f]
	/usr/lib/x86_64-linux-gnu/libgstreamer-1.0.so.0(gst_pad_forward+0x1c7) [0x7f5769f3f857]
	/usr/lib/x86_64-linux-gnu/libgstreamer-1.0.so.0(gst_pad_event_default+0xfe) [0x7f5769f3f98e]
	/usr/lib/x86_64-linux-gnu/libgstreamer-1.0.so.0(+0x5f6db) [0x7f5769f396db]
	/usr/lib/x86_64-linux-gnu/libgstreamer-1.0.so.0(+0x5fec4) [0x7f5769f39ec4]
	/usr/lib/x86_64-linux-gnu/libgstreamer-1.0.so.0(+0x60348) [0x7f5769f3a348]
	/usr/lib/x86_64-linux-gnu/libgstreamer-1.0.so.0(+0x5e632) [0x7f5769f38632]
	/usr/lib/x86_64-linux-gnu/libgstreamer-1.0.so.0(gst_pad_push_event+0x378) [0x7f5769f42618]
	/usr/lib/x86_64-linux-gnu/libgstaudio-1.0.so.0(+0x19fdb) [0x7f576acfdfdb]
	/usr/lib/x86_64-linux-gnu/libgstaudio-1.0.so.0(+0x1ef7c) [0x7f576ad02f7c]
	/usr/lib/x86_64-linux-gnu/libgstreamer-1.0.so.0(+0x5f6db) [0x7f5769f396db]
	/usr/lib/x86_64-linux-gnu/libgstreamer-1.0.so.0(+0x5fec4) [0x7f5769f39ec4]
	/usr/lib/x86_64-linux-gnu/libgstreamer-1.0.so.0(+0x60348) [0x7f5769f3a348]
	/usr/lib/x86_64-linux-gnu/libgstreamer-1.0.so.0(+0x5e632) [0x7f5769f38632]
	/usr/lib/x86_64-linux-gnu/libgstreamer-1.0.so.0(gst_pad_push_event+0x378) [0x7f5769f42618]
	/usr/lib/x86_64-linux-gnu/libgstbase-1.0.so.0(+0x187da) [0x7f576a1f67da]
	/usr/lib/x86_64-linux-gnu/libgstreamer-1.0.so.0(+0x8e549) [0x7f5769f68549]
	/lib/x86_64-linux-gnu/libglib-2.0.so.0(+0x6e89c) [0x7f577e6b289c]
	/lib/x86_64-linux-gnu/libglib-2.0.so.0(+0x6df15) [0x7f577e6b1f15]
	/lib/x86_64-linux-gnu/libpthread.so.0(+0x8182) [0x7f5781bc1182]
	/lib/x86_64-linux-gnu/libc.so.6(clone+0x6d) [0x7f57818ee30d]

Debug info from gdb:

[Error 19:04:40.694] GStreamer resource error: NotFound
Could not attach to process.  If your uid matches the uid of the target
process, check the setting of /proc/sys/kernel/yama/ptrace_scope, or try
again as the root user.  For more details, see /etc/sysctl.d/10-ptrace.conf
ptrace: Operation not permitted.
No threads.

=================================================================
Got a SIGABRT while executing native code. This usually indicates
a fatal error in the mono runtime or one of the native libraries 
used by your application.
=================================================================