fixed another return FALSE in a function returning a pointer (patch 545046)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@15216 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/dibutils.cpp

@@ -305,7 +305,7 @@ PDIB wxDibReadBitmapInfo(HFILE fh)
     }
 
     if (sizeof(bi) != _lread(fh,(LPSTR)&bi,sizeof(bi)))
-        return FALSE;
+        return NULL;
 
     /*
      *  what type of bitmap info is this?