gdi32: Check header pointer in CreateDIBitmap.

dlls/gdi32/dib.c

@@ -1097,6 +1097,8 @@ HBITMAP WINAPI CreateDIBitmap( HDC hdc, const BITMAPINFOHEADER *header,
     DWORD compr, size;
     DC *dc;
 
+    if (!header) return 0;
+
     if (DIB_GetBitmapInfo( header, &width, &height, &planes, &bpp, &compr, &size ) == -1) return 0;
     
     if (width < 0)

dlls/gdi32/tests/bitmap.c

@@ -145,6 +145,11 @@ static void test_createdibitmap(void)
     bmih.biBitCount = 32;
     bmih.biCompression = BI_RGB;
 
+    hbm = CreateDIBitmap(hdc, NULL, CBM_INIT, NULL, NULL, 0);
+    ok(hbm == NULL, "CreateDIBitmap should fail\n");
+    hbm = CreateDIBitmap(hdc, NULL, 0, NULL, NULL, 0);
+    ok(hbm == NULL, "CreateDIBitmap should fail\n");
+
     /* First create an un-initialised bitmap.  The depth of the bitmap
        should match that of the hdc and not that supplied in bmih.
     */