Fix panic when importing non-existent GitHub integration

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This change cleans up debug logging messages in the GitLab GitHub integration code. The developer removed redundant "[DEBUG]" prefixes from log messages since the logging system already indicates the debug level, and simplified one error message to only show the project name instead of including additional details that might not always be available. This makes the logs cleaner and more consistent while maintaining the same functionality.

Fixes #6393 (closed)