Description of problem:
It may happen that the received clipboard data is empty, but
if it's of type image/bmp, gtk+ will crash:

gdk_property_change: 00030AD4 GDK_SELECTION image/bmp REPLACE 8*0 bits:
... delayed rendering
gdk_selection_send_notify_for_display: 00030AD4 CLIPBOARD image/bmp
GDK_SELECTION (no-op)
_gdk_win32_selection_convert_to_dib: 1252003C image/bmp

Program received signal SIGSEGV, Segmentation fault.
0x749a9f40 in msvcrt!memmove () from C:\Windows\syswow64\msvcrt.dll

Thread 1 (Thread 2248.0x1b34):
target=0xc07b) at gdkselection-win32.c:1292
at gdkevents-win32.c:3498
wparam=8, lparam=0) at gdkevents-win32.c:232
message=773, wparam=8, lparam=0)
    at gdkevents-win32.c:263
C:\Windows\syswow64\user32.dll
C:\Users\rugoosse\AppData\Local\virt-viewer\bin\libpangocairo-1.0-0.dll
wparam=0, lparam=-1687549457)
    at gdkevents-win32.c:248
C:\Users\rugoosse\AppData\Local\virt-viewer\bin\libpangocairo-1.0-0.dll

Version-Release number of selected component (if applicable):
rhevm-spice-client-x86-cab-3.3-11.el6_5

How reproducible:
easily

Steps to Reproduce:
On the guest:
1.	Create a screenshot of the desktop in the guest
2.	Copy to clipboard
3.	Close the screenshot dialog
On the Windows client:
4.	Paste in Paint (Windows) => Paint is performing a long task…
5.	Close paint, are you sure to force close => yes (note that during the Paint task the VDI freezes as well)
6.	After paint is closed the VDI responds again, now create new screenshot
On the guest:
7.	Press copy to clipboard and note it freezes

Actual results:
Remote-viewer throw a segmentation fault

Expected results:
No segfault

Additional info:
https://bugzilla.gnome.org/show_bug.cgi?id=728745