fix #11401: remove deleted tree notes from selected set
fix #10561: NPE from Activities window kymograph link

the confusion arose from the group view not containing an
experimenter node
move deleted tree node deselection into browser component

suggested by @joshmoore
Merge pull request #1442 from mtbc/rebased/develop/activities-npe-10561

fix #10561: make user object getting robust to no experimenter in tree (rebased onto develop)
Merge pull request #1435 from mtbc/deleted-container-11401

fix #11401: remove deleted tree nodes from set of selected nodes (rebase)