Transcoder: Fix codec config error with single frame video

Add default frame rate config in order to successfully
configure the encoder when frame rate information is
missing, such as for single-frame videos.

Bug: 175641397
Test: Unit tests
Change-Id: I2bab3534d5de5df41e5309049cb8e1249cf955d1
diff --git a/media/libmediatranscoding/transcoder/benchmark/MediaTrackTranscoderBenchmark.cpp b/media/libmediatranscoding/transcoder/benchmark/MediaTrackTranscoderBenchmark.cpp
index 351d80b..d6ed2c6 100644
--- a/media/libmediatranscoding/transcoder/benchmark/MediaTrackTranscoderBenchmark.cpp
+++ b/media/libmediatranscoding/transcoder/benchmark/MediaTrackTranscoderBenchmark.cpp
@@ -167,6 +167,10 @@
         return AMEDIA_OK;
     }
 
+    media_status_t unselectTrack(int trackIndex __unused) override {
+        return AMEDIA_ERROR_UNSUPPORTED;
+    }
+
     media_status_t setEnforceSequentialAccess(bool enforce __unused) override { return AMEDIA_OK; }
 
     media_status_t getEstimatedBitrateForTrack(int trackIndex __unused,