surface: don't unset width and height in finalize

During surface finalization we may not have received a new buffer,
resetting width and height in this case is wrong since we display the
old buffer in this case.

types/wlr_surface.c

@@ -174,17 +174,17 @@ static void surface_state_finalize(struct wlr_surface *surface,
 		}
 	}
 
-	if (state->buffer_resource != NULL) {
 	if (state->viewport.has_dst) {
+		if (state->buffer_width == 0 && state->buffer_height == 0) {
+			state->width = state->height = 0;
+		} else {
 			state->width = state->viewport.dst_width;
 			state->height = state->viewport.dst_height;
+		}
 	} else {
 		surface_state_viewport_src_size(state,
 			&state->width, &state->height);
 	}
-	} else {
-		state->width = state->height = 0;
-	}
 
 	pixman_region32_intersect_rect(&state->surface_damage,
 		&state->surface_damage, 0, 0, state->width, state->height);