lavfi: add error handling to filter_samples().

libavfilter/af_amix.c

libavfilter/af_asyncts.c

libavfilter/af_channelmap.c

libavfilter/af_channelsplit.c

libavfilter/af_join.c

libavfilter/af_resample.c

libavfilter/asink_anullsink.c

libavfilter/audio.c

libavfilter/audio.h

libavfilter/avfilter.h

libavfilter/buffersink.c

libavfilter/buffersrc.c

libavfilter/fifo.c

libavfilter/internal.h

libavfilter/split.c