fix NULL pointer crash in clipboard.c

[Rein Klazes]

Hi,

Fix for bug #2148.

Changelog:
	dlls/x11drv	: clipboard.c
	Do not crash if the clipboard format is unknown.

Rein.
-- 
Rein Klazes
rklazes at xs4all.nl
-------------- next part --------------
--- wine/dlls/x11drv/clipboard.c	2004-02-20 06:43:00.000000000 +0100
+++ mywine/dlls/x11drv/clipboard.c	2004-04-04 19:48:56.000000000 +0200
@@ -369,6 +369,10 @@
 
 	lpFormat = lpFormat->NextFormat;
     }
+    if (!lpFormat) {
+        ERR("unknown format: %d\n", wID);
+        return 0;
+    }
     if (!lpFormat->drvData) intern_atoms();
     return lpFormat;
 }
@@ -1656,7 +1660,7 @@
 
         lpFormat = X11DRV_CLIPBOARD_LookupFormat(wFormat);
 
-        if (lpFormat->drvData)
+        if (lpFormat && lpFormat->drvData)
         {
     	    DWORD i;
 	    UINT alias;