Codec2 decoders: Invalidate allocated graphic buffer in stop()

Bug: 243583691
Test: atest CtsMediaV2TestCases -- --module-arg \
CtsMediaV2TestCases:instrumentation-arg:codec-prefix:=c2.android.

Change-Id: I312c106350b2eb072f0e6f2f9a83f16eb8424cb2
diff --git a/media/codec2/components/hevc/C2SoftHevcDec.cpp b/media/codec2/components/hevc/C2SoftHevcDec.cpp
index a27c218..15d6dcd 100644
--- a/media/codec2/components/hevc/C2SoftHevcDec.cpp
+++ b/media/codec2/components/hevc/C2SoftHevcDec.cpp
@@ -664,6 +664,9 @@
 void C2SoftHevcDec::resetPlugin() {
     mSignalledOutputEos = false;
     mTimeStart = mTimeEnd = systemTime();
+    if (mOutBlock) {
+        mOutBlock.reset();
+    }
 }
 
 status_t C2SoftHevcDec::deleteDecoder() {