avcodec/imm5: Dont pass EAGAIN on as is

Fixes: Assertion consumed != (-(11)) failed at libavcodec/decode.c:465
Fixes: 471587358/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_IMM5_fuzzer-4737412376100864

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

libavcodec/imm5.c

@@ -136,6 +136,8 @@ static int imm5_decode_frame(AVCodecContext *avctx, AVFrame *frame,
     }
 
     ret = avcodec_receive_frame(codec_avctx, frame);
+    if (ret == AVERROR(EAGAIN))
+        return avpkt->size;
     if (ret < 0)
         return ret;