avcodec/faxcompr: Check if bits are available before reading in cmode == 9 || cmode == 10

Fixes: Timeout
Fixes: 34950/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_TIFF_fuzzer-5686764151898112

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/faxcompr.c

@@ -304,7 +304,10 @@ static int decode_group3_2d_line(AVCodecContext *avctx, GetBitContext *gb,
                 mode = !mode;
             }
         } else if (cmode == 9 || cmode == 10) {
-            int xxx = get_bits(gb, 3);
+            int xxx;
+            if (get_bits_left(gb) < 3)
+                return AVERROR_INVALIDDATA;
+            xxx = get_bits(gb, 3);
             if (cmode == 9 && xxx == 7) {
                 int ret;
                 int pix_left = width - offs;