go2meeting: disallow tile dimensions that are not multiple of 16

Original decoder seems to always use 176x128 tiles anyway and this helps
avoiding lots of issues with odd tile sizes in fuzzed files.

Signed-off-by: Anton Khirnov <anton@khirnov.net>

libavcodec/g2meet.c

@@ -712,7 +712,8 @@ static int g2m_decode_frame(AVCodecContext *avctx, void *data,
             }
             c->tile_width  = bytestream2_get_be32(&bc);
             c->tile_height = bytestream2_get_be32(&bc);
-            if (!c->tile_width || !c->tile_height) {
+            if (!c->tile_width || !c->tile_height ||
+                ((c->tile_width | c->tile_height) & 0xF)) {
                 av_log(avctx, AV_LOG_ERROR,
                        "Invalid tile dimensions %dx%d\n",
                        c->tile_width, c->tile_height);