Stop the parser from backtracking (backport #9309)

[mergify]

Fixes https://github.com/Exiv2/exiv2/security/advisories/GHSA-fgw8-p7pr-37cp, an infinite loop found by OSS-Fuzz.

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This is an automatic backport of pull request #9309 done by Mergify.

[mergify]

Cherry-pick of 9373015 has failed:

On branch mergify/bp/main/pr-9309
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You are currently cherry-picking commit 9373015d.
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Unmerged paths:
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	both modified:   src/quicktimevideo.cpp

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