Catch exceptions (seen in production) and log them.

* For now, generating error as before so that we can log more
  information about them and fix them.

Change-Id: I9e5b67603dab4e3c2c65f53473af4d1e22ac034d
WTS: Skip auto-inserted tags for empty nodes with 0-wide subtree DSR

* Even in edit mode (the default mode), auto-inserted start/end
  tags can be omitted for a node as long as it has no children
  and the dsr range for child subtree is zero.

* Eliminates a whole bunch of artificial wt2wt (and associated
  selser) failures from parser tests.

Bug: 62569
Change-Id: Iacb1ba2f753d47595cc408a2326a2d6696745520
Merge "Catch exceptions (seen in production) and log them."
Merge "WTS: Skip auto-inserted tags for empty nodes with 0-wide subtree DSR"