HLS: Ignore empty NALU to avoid error. v6.0.65 #2605

Job	Run time
multiple-arch-aarch64	2m 12s
multiple-arch-armv7	2m 10s
cygwin64-cache	1m 57s
utest-regression-blackbox-test	2m 10s
fast	1s
cygwin64	1s
build-ubuntu18	1s
build-ubuntu16	1s
build-centos7	1s
build-ubuntu20	1s
build-cross-arm	1s
build-cross-aarch64	1s
coverage	1s
multiple-arch-amd64	1s
test-done	1s
	8m 40s

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