Handle missing channel names without error spew.

We just default to empty string instead.

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14609 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd
Don't try to pull for input when the queue is null

This fixes a bug where DataProcessors could error out with a
NullPointerException when they get added/removed from the processing pipeline
and a new acquisition is started.

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14610 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd
GUI API: Added comment to DataProcessor to make clear that the constructor should not be overridden

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14611 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd
PositionList: Added missing header to PositionTableModel

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14612 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd
PositionList: Added missing header to PositionTableModel

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14613 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd