[TIFF writing] Fix an assumption that was broken by a prior commit.

r14653 ensured that we never created a TaggedImage with null metadata, to fix
a downstream problem. However, the fixIndexMap() function explicitly checks for
null metadata to detect placeholder images. It has now been modified to also
check for zero-length metadata and also treat that as a placeholder; in
practice I do not think we will ever have real images with zero-length
metadata, so this should be safe, especially as fixIndexMap() is rarely
called.

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14802 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd
ASIdiSPIM: comment updates only

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14803 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd
Gaussian plugin: refctoring only: split out some code from bloated DataColletion form

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14804 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd
Gaussian plugin: Remove a number of compiler warnings

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14805 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd
Gaussian: refactoring, there should be no functional changes

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14806 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd
Gaussian: missed a file in previous commit

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14807 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd
Gaussian: adding three more files mossed in previous commit

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14808 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd
Navigator: more work on acquisitions and cleanup of display code

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14809 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd
ASIdiSPIM: add button for adjusting calibration offset only (based on current position)

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14810 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd
Gaussian plugin: started work on new spot linking code

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14811 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd
Gaussian: cleanup for superfluous lines

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14812 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd