Don't crash if freeing a hardware surface after the video mode has been

reset.  Fortunately we keep track of the video memory internally.

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%40103

src/video/dga/SDL_dgavideo.c

@@ -740,11 +740,12 @@ static void DGA_FreeHWSurface(_THIS, SDL_Surface *surface)
 	vidmem_bucket *bucket, *freeable;
 
 	/* Look for the bucket in the current list */
-	bucket = (vidmem_bucket *)surface->hwdata;
-	if ( (bucket == NULL) || ! bucket->used ) {
-		return;
+	for ( bucket=&surfaces; bucket; bucket=bucket->next ) {
+		if ( bucket == (vidmem_bucket *)surface->hwdata ) {
+			break;
 		}
-
+	}
+	if ( bucket && bucket->used ) {
 		/* Add the memory back to the total */
 #ifdef DGA_DEBUG
 	printf("Freeing bucket of %d bytes\n", bucket->size);
@@ -777,6 +778,7 @@ static void DGA_FreeHWSurface(_THIS, SDL_Surface *surface)
 			}
 			free(freeable);
 		}
+	}
 	surface->pixels = NULL;
 	surface->hwdata = NULL;
 }