maybe the signal lives longer than the display

this avoids the crash for me:

diff --git a/src/vnc-display.vala b/src/vnc-display.vala
index 8cf5d42..e78c474 100644
--- a/src/vnc-display.vala
+++ b/src/vnc-display.vala
@@ -70,9 +70,7 @@
             display.close ();
         });
 
-        this.notify["config"].connect (() => {
-            config.sync_properties (display, sync_properties);
-        });
+        this.config.sync_properties (display, sync_properties);
     }
 
     public VncDisplay (BoxConfig config, string host, int port) {

(In reply to Pavel Grunt from comment #1)
> maybe the signal lives longer than the display

Hmm.. that is very much possible. I'll see if we can use g_signal_connect_object() from vala.

> this avoids the crash for me:

Thanks for helping out with investigation. :)

Looking at the backtrace, i don't think that's the issue here but it's just that not connecting to the signal, means this code doesn't get called:

+ Trace 236088

There is still some issue of 'readonly' property of VNC display not getting loaded after it's changed via properties launched from overview but that would a separate bug.

---
commit: 262cfe580c18cdbbbae5e3e8c6523ecf9f444b81
Date:   Wed Mar 16 16:54:06 2016 +0000

    box-config: SyncProperty -> SavedProperty
    
    SyncProperty is a silly and confusing name.

commit: 498461a841545a20488f3a08bca4b79cd2185a83
Date:   Wed Mar 16 15:37:14 2016 +0000

    box-config: Don't access passed array after method returns
    
    Seems we can't rely on the passed array of structs to be around in a
    closure and get a crash.
    
    This patch fixes a crash when going back to overview from a VNC display.

commit: fe4f075a1f4e3feb515c81b2c03c499c1317f32b
Date:   Wed Mar 16 16:03:27 2016 +0000

    machine: Add a null check
    
    The 'window' is already gone when display is hidden as part of Boxes
    shutdown so accessing it only crashes Boxes on exit.

commit: 031b7918dee1ff016d74a69515f9cdbabc4b6b31
Date:   Wed Mar 16 16:28:40 2016 +0000

    display: config property now protected
    
    It's only set by subclasses anyway.
    
commit: 447d66dfbb6ea372b1fb48f545a5de675463f2c5
Date:   Wed Mar 16 16:30:41 2016 +0000

    spice,vnc: Simplify setting up syncing of properties
    
    Instead of hooking-up to 'config' property changes to set-up syncing of
    saved properties of display, let's just do that already after
    initializing 'config' property (which happens once anyway).

Filed bug#763772 for Read-only not getting saved/loaded.

*** Bug 767490 has been marked as a duplicate of this bug. ***