Fix out-of-bounds read in CrwMap::decode0x0805 (backport #3462)

[mergify]

I've created GHSA-9mxq-4j5g-5wrp for this, but it's a very minor bug and I'm only able to reproduce with our fuzz target, not with the exiv2 command line application. When creating the string, CrwMap::decode0x0805 might read off the end of the buffer. It stops reading when it gets to the first '\0' byte.

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This is an automatic backport of pull request #3462 done by Mergify.

[mergify]

Cherry-pick of 5b8f1f4 has failed:

On branch mergify/bp/main/pr-3462
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	both modified:   src/crwimage_int.cpp

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