Allow deletion of multiple tags without moving the mouse

The dialog used the mouse move event to sent the m_deleteCandidate,
and then set m_deleteCandidate = 0. On trying to delete the next
tag, the deleteTag() function would assert as m_deleteCandidate was 0

m_deleteCandidate is now set to next tag after deletion of a tag.

BUG: 248689
REVIEW: 102111