Avoid infinite loops in block decoding

Fixes: 1921/clusterfuzz-testcase-minimized-5480510065213440

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg

libAACdec/src/block.cpp

@@ -372,6 +372,9 @@ AAC_DECODER_ERROR CBlock_ReadSectionData(
       }
 
       sect_len += sect_len_incr;
+      if (sect_len <= 0) {
+         return AAC_DEC_PARSE_ERROR;
+      }
 
       top = band + sect_len;