contrib: fix for macOS deployment build failing on Qt translations even though it is optional. #33358

From what I deciphered reading the line https://github.com/bitcoin/bitcoin/blob/master/contrib/macdeploy/macdeployqtplus#L390 is that qt translations are optional to have hence we should be able to build without it but the case where the flag translations_dir falls back to its default Null value it raises this error. I have moved the code which adds language files under the if statement that first checks if the value of the flag is not Null before referencing it. This PR assumes that having Qt translations is optional however this statement requires a second opinion. Build completes successfully post this change with default value of the flag.

<img width="754" height="372" alt="Screenshot 2025-09-10 at 9 11 25 PM" src="https://github.com/user-attachments/assets/61b74a88-465b-4719-b8f4-dcf165c6ad79" />

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For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/33358.

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Thanks. You'll need to remove the merge commit here. Can you change the commit message to something more like: contrib: fix using macdeploy script without translations.

@fanquake yes!, done.

gui: Avoid pathological QT text/markdown behavior... during text selection by only setting plaintext mime data. @amishhaa looks like you've got a partial commit message from a prior commit in this repo, as part of your commit message?

@fanquake, sorry for the delay! fixed.

@amishhaa

Would you mind sharing the steps to reproduce the failure?

@hebasto yes! So I was following the general steps to set up app on macos however I didn't download any qt translations presuming it was optional from the comment linkedin in PR, so to reproduce if you have translation directories in place ull need to delete them and then try to build the file, otherwise don't download it at all and try to build it. It should fail on that flag as translations dir was never downloaded.

Closed this PR due to some local branching issues. Reopened #33482 with a clean working tree. (cc: @hebasto, @fanquake )