Description of problem:
 in regular operation not really sure 

still troubleshooting 

Version-Release number of selected component:
gnome-shell-3.14.3-1.fc21

Additional info:
reporter:       libreport-2.3.0
backtrace_rating: 4
cmdline:        /usr/bin/gnome-shell
crash_function: window_backed_app_get_window
executable:     /usr/bin/gnome-shell
kernel:         3.17.7-300.fc21.x86_64
runlevel:       N 5
type:           CCpp
uid:            1000

Truncated backtrace:
Thread no. 1 (10 frames)
 #4 window_backed_app_get_window at shell-app.c:152
 #5 shell_app_launch at shell-app.c:1330
 #6 shell_app_activate_full at shell-app.c:663
 #7 ffi_call_unix64 at ../src/x86/unix64.S:76
 #8 ffi_call at ../src/x86/ffi64.c:525
 #9 gjs_invoke_c_function at gi/function.cpp:972
 #10 function_call at gi/function.cpp:1294
 #11 CallJSNative at /usr/src/debug/mozjs-24.2.0/js/src/jscntxtinlines.h:321
 #12 js::Invoke at /usr/src/debug/mozjs-24.2.0/js/src/vm/Interpreter.cpp:474
 #13 Interpret at /usr/src/debug/mozjs-24.2.0/js/src/vm/Interpreter.cpp:2298

Potential duplicate: bug 905914