avcodec/tiff: Check for multiple geo key directories

Fixes memleak
Fixes: 826/clusterfuzz-testcase-5316921379520512

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

libavcodec/tiff.c

@@ -1045,6 +1045,10 @@ static int tiff_decode_tag(TiffContext *s, AVFrame *frame)
         ADD_METADATA(count, "ModelTiepointTag", NULL);
         break;
     case TIFF_GEO_KEY_DIRECTORY:
+        if (s->geotag_count) {
+            avpriv_request_sample(s->avctx, "Multiple geo key directories\n");
+            return AVERROR_INVALIDDATA;
+        }
         ADD_METADATA(1, "GeoTIFF_Version", NULL);
         ADD_METADATA(2, "GeoTIFF_Key_Revision", ".");
         s->geotag_count   = ff_tget_short(&s->gb, s->le);