Do set empty tooltip if it is pinned.

git-svn-id: https://svn.code.sf.net/p/genoviz/code/trunk@15076 80d5a9c2-7d8c-4c9f-9369-4e03bca4d2bd
Do set properties to null in preferred location is set.

git-svn-id: https://svn.code.sf.net/p/genoviz/code/trunk@15077 80d5a9c2-7d8c-4c9f-9369-4e03bca4d2bd
Do not show exon properties in tooltip.

git-svn-id: https://svn.code.sf.net/p/genoviz/code/trunk@15078 80d5a9c2-7d8c-4c9f-9369-4e03bca4d2bd
Merge remote-tracking branch 'upstream'