tools/target_dec_fuzzer: Fix parser_avctx memleak on error path

Fixes: oss-fuzz issue 9195

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

tools/target_dec_fuzzer.c

@@ -190,6 +190,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
     int res = avcodec_open2(ctx, c, NULL);
     if (res < 0) {
         av_free(ctx);
+        av_free(parser_avctx);
         return 0; // Failure of avcodec_open2() does not imply that a issue was found
     }