We have the following problems in the Merge Diff Preference Page.
1. "Compare using external Tool" is not checked and "Path to Diff Tool Executable" is empty and you press "Apply" will result in pop-up dialog not showing. We should not care to validate exec path field since it will not be used.
2. "Path to Diff Tool Executable" does not handle windows paths very well. We need to handle windows paths too :-)