Fix #1465: skip mixed nalu leading pictures when beginning a stream

6 jobs for !2019 with fix_1465 in 14 minutes and 37 seconds
detached
Status Job ID Name Coverage
  Build
passed #20500
macos
build_macos

00:03:49

passed #20501
ubuntu1604
build_ubuntu1604

00:05:34

passed #20502
ubuntu1804
build_ubuntu1804

00:05:21

passed #20503
ubuntu1804-gcc8
build_ubuntu1804-gcc8

00:05:58

passed #20504
vc191x
build_vc191x

00:14:35

passed #20505
vc192x
build_vc192x

00:13:18