GB: Fix SGB recording dimensions (fixes #1055)

src/gb/core.c

@@ -281,7 +281,9 @@ static void _GBCoreSetAVStream(struct mCore* core, struct mAVStream* stream) {
 	struct GB* gb = core->board;
 	gb->stream = stream;
 	if (stream && stream->videoDimensionsChanged) {
-		stream->videoDimensionsChanged(stream, GB_VIDEO_HORIZONTAL_PIXELS, GB_VIDEO_VERTICAL_PIXELS);
+		unsigned width, height;
+		core->desiredVideoDimensions(core, &width, &height);
+		stream->videoDimensionsChanged(stream, width, height);
 	}
 }