gnome-software-3.24.3-1.fc26.x86_64

+ Trace 237490

$1 = (GError_autoptr) 0x5571c0429600
(gdb) p error->
code     domain   message  
(gdb) p error->code 
$2 = 19
(gdb) p error->domain 
$3 = 289
(gdb) p error->message 
$4 = (gchar *) 0x5571c1527ca0 "Operation was cancelled"
(gdb) list
191		}
192	
193		/* no results */
194		if (gs_app_list_length (list) == 0) {
195			g_debug ("no installed updates to show");
196			gtk_stack_set_visible_child_name (GTK_STACK (dialog->stack), "empty");
197			return;
198		}
199	
200		/* set the header title using any one of the applications */
(gdb) p list
$5 = (GsAppList_autoptr) 0x0

My guess is that:
175 ↦       gs_stop_spinner (GTK_SPINNER (dialog->spinner));•
is poking at memory it shouldn't.

If the call is cancelled because the dialog was destroyed, you're doing something bad. That's probably wasn't breaking the error as well (the error code isn't GS_PLUGIN_ERROR_CANCELLED/2), and the list is NULL despite being checked for NULL a second earlier.