Remove the assertion when there is no source surface.
[wine] / dlls /
drwxr-xr-x   ..
-rw-r--r-- 23 .cvsignore
-rw-r--r-- 2154 Makedll.rules.in
-rw-r--r-- 10180 Makefile.in
drwxr-xr-x - advapi32
drwxr-xr-x - avifil32
drwxr-xr-x - comctl32
drwxr-xr-x - commdlg
drwxr-xr-x - crtdll
drwxr-xr-x - dciman32
drwxr-xr-x - ddraw
drwxr-xr-x - dinput
drwxr-xr-x - display
drwxr-xr-x - dplayx
drwxr-xr-x - dsound
drwxr-xr-x - gdi
drwxr-xr-x - icmp
drwxr-xr-x - imagehlp
drwxr-xr-x - imm32
drwxr-xr-x - lzexpand
drwxr-xr-x - mouse
drwxr-xr-x - mpr
drwxr-xr-x - msacm
drwxr-xr-x - msacm32
drwxr-xr-x - msnet32
drwxr-xr-x - msvideo
drwxr-xr-x - ntdll
drwxr-xr-x - odbc32
drwxr-xr-x - ole32
drwxr-xr-x - oleaut32
drwxr-xr-x - olecli
drwxr-xr-x - oledlg
drwxr-xr-x - olepro32
drwxr-xr-x - olesvr
drwxr-xr-x - psapi
drwxr-xr-x - rasapi32
drwxr-xr-x - setupx
drwxr-xr-x - shell32
drwxr-xr-x - sound
drwxr-xr-x - stress
drwxr-xr-x - tapi32
drwxr-xr-x - ttydrv
drwxr-xr-x - urlmon
drwxr-xr-x - user
drwxr-xr-x - version
drwxr-xr-x - win32s
drwxr-xr-x - win87em
drwxr-xr-x - winaspi
drwxr-xr-x - windebug
drwxr-xr-x - wing
drwxr-xr-x - wininet
drwxr-xr-x - winmm
drwxr-xr-x - winsock
drwxr-xr-x - winspool
drwxr-xr-x - x11drv