"Add path substitution" dialog should not create a new row if "from" and "to" is exactly same

[sparkhi]

There is a way to add path substitution using a small dialog. The dialog only has OK button. If someone opens the dialog and presses the "OK" button without entering any values. A new blank line is added to the Path Substitutions table. This is unnecessary. If both values are blank, pressing "OK" should just be treated as pressing "Cancel"

By extension, if both values "from" and "to" are exactly same, the substitution is meaningless, in such case as well, pressing "OK" can be treated as cancel. However, in this case if the user does not realise that this happened because the paths are same, they might be baffled as to why new row is not added, so this extension case needs to be carefully considered