When entering a tag that already exists, the tag should not be duplicated in photo_tags table. (Correctly detected as already existing in tags table).
Steps to reproduce the issue
In album mode (right click->Tag) Add a given tag to a test image. Close and refresh, open tag dialog again, and hit "set" without changing anything. Tag now appears twice.
Currently uses the current microtime, zero-padded right, to generate IDs (primary keys). This has the potential to eventually try to assign duplicate values.