Fix NPE when opening very large changes

If a change has so many files that the PatchTable is drawn
incrementally with a progress meter, the table inside of it
isn't available to receive events until the rendering is done.
Delay adding handlers or registering navigation keys until then.

Change-Id: I76adf0f8a44ac1df6dd83f0ac4add5de6ead7cfd
Signed-off-by: Shawn O. Pearce <sop@google.com>
1 file changed