Please describe the problem:
In case meld is not installed and either the "diff" or the "sync directory" function is selected. Nothing happens, i.e. the user doesn't actually know what's wrong since no error message in the gui interface appears..

Steps to reproduce:
1. Make sure meld is not installed.
2. Start gnome-commander in a terminal.
3. Select either the "diff" or "sync directory" function.
4. Have a look at the shell output


Actual results:
1. Nothing in the gui interface.
2. In the terminal interface one is told that meld was missing.

Expected results:
An error message should pop up that tells one that meld is not installed / could not be found.

Does this happen every time?
Yes

Other information:
However, starting gnome-commander in a terminal and looking at the shell output after selecting the "diff" or "sync directory" function reveals that meld is missing.

After installing meld everything works just fine.