GalleryAdults: Fix app crash

[cuong-tran]

Fetch pages sequentially to avoid concurrent modification of the list

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String eu.kanade.tachiyomi.multisrc.galleryadults.Genre.getName()' on a null object reference

Checklist:

• Updated extVersionCode value in build.gradle for individual extensions
• Updated overrideVersionCode or baseVersionCode as needed for all multisrc extensions
• Referenced all related issues in the PR body (e.g. "Closes #xyz")
• Added the isNsfw = true flag in build.gradle when appropriate
• Have not changed source names
• Have explicitly kept the id if a source's name or language were changed
• Have tested the modifications by compiling and running the extension through Android Studio
• Have removed web_hi_res_512.png when adding a new extension

[Copilot]

Pull request overview

This PR fixes an app crash caused by a NullPointerException when attempting to access Genre names. The root cause was concurrent modification of the tags list during parallel page fetching. The fix changes tag fetching from concurrent to sequential execution to prevent race conditions.

Changes:

• Replaced concurrent tag fetching (using runBlocking, Job, and joinAll) with sequential fetching using forEach
• Added proper resource cleanup with .use { } for HTTP response handling
• Improved exception handling with finally block to ensure tagsFetchAttempt is always incremented
• Applied code style improvements (expression body functions, formatting)
• Incremented baseVersionCode from 5 to 6

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
lib-multisrc/galleryadults/src/eu/kanade/tachiyomi/multisrc/galleryadults/GalleryAdults.kt	Fixed concurrent modification bug by switching to sequential tag fetching; added proper resource cleanup; applied code style improvements
lib-multisrc/galleryadults/build.gradle.kts	Incremented baseVersionCode to 6 to reflect the bug fix

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