avcodec/vp3: Check for end of input in 2 places of vp4_unpack_macroblocks()

Fixes: Timeout (82sec -> 1sec)
Fixes: 16411/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VP3_fuzzer-5166958151991296

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

libavcodec/vp3.c

@@ -710,6 +710,8 @@ static int vp4_unpack_macroblocks(Vp3DecodeContext *s, GetBitContext *gb)
     has_partial = 0;
     bit         = get_bits1(gb);
     for (i = 0; i < s->yuv_macroblock_count; i += current_run) {
+        if (get_bits_left(gb) <= 0)
+            return AVERROR_INVALIDDATA;
         current_run = vp4_get_mb_count(s, gb);
         if (current_run > s->yuv_macroblock_count - i)
             return -1;
@@ -719,6 +721,8 @@ static int vp4_unpack_macroblocks(Vp3DecodeContext *s, GetBitContext *gb)
     }
 
     if (has_partial) {
+        if (get_bits_left(gb) <= 0)
+            return AVERROR_INVALIDDATA;
         bit  = get_bits1(gb);
         current_run = vp4_get_mb_count(s, gb);
         for (i = 0; i < s->yuv_macroblock_count; i++) {