#403 comapre against predecessor with external tool fails for checked-outs

[Thomas Bark]

With version 2.2.42 following problem occurs (at least in UCM):
When trying to "compare against predecessor" with a checked-out file, and external tool is checked (e.g. kdiff3), it tries to compare version 0 of the branch, on both side, which fails, as these are always identical.

Internal compare works as expected.
Most probably its a side effect of the bug #388 solution.

[Thomas Bark]

The fault was applicable for "compare to other view (external)" too.

[bug_403_extdiff 8702bda] Bug #403 solved