obu: don't abort OBU_REDUNDANT_FRAME_HDR if no frame header has been parsed

Parse and use it instead.

Signed-off-by: James Almer <jamrial@gmail.com>
8 jobs for master in 2 minutes and 15 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Build
passed build-debian #5260
debian amd64

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passed build-debian-aarch64 #5264
aarch64 debian

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passed build-debian-aarch64-clang-5 #5265
aarch64 clang5 debian

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passed build-debian-static #5261
debian amd64

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passed build-debian-werror #5267
aarch64 debian

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passed build-macos #5266
macos

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passed build-win32 #5262
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passed build-win64 #5263
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