Comment 2 for bug 1197104

StacktraceTop:
 wnck_window_get_xid (window=0x9b9b20) at window.c:860
 unity_webapps_interest_tracker_ensure_interest_state (tracker=0x8e0e60, interest_id=6) at interest-tracking/unity-webapps-interest-tracker.c:247
 ffi_call_unix64 () at ../src/x86/unix64.S:76
 ffi_call (cif=cif@entry=0x7fff0cf081d0, fn=0x40cba0 <unity_webapps_interest_tracker_interest_is_active_changed>, rvalue=0x7fff0cf08140, avalue=avalue@entry=0x7fff0cf080e0) at ../src/x86/ffi64.c:522
 g_cclosure_marshal_generic (closure=0x962e70, return_gvalue=0x0, n_param_values=<optimized out>, param_values=<optimized out>, invocation_hint=<optimized out>, marshal_data=0x0) at /build/buildd/glib2.0-2.37.3/./gobject/gclosure.c:1454