TERMINAL EMULATOR NOT SET

One trival problem almost to silly to mention, but which has puzzled some people is when right clicking a folder containing the program to be run and clicking on 'open in terminal' expecting to see the terminal window open and to be able to type in the command line to run that program -  it wont open and displays the below box

Notice terminal emulator was blank - so just type in 'x-terminal-emulator' - whether you see this sitation and perceive it as a problem depends on how you are in the habit of launching your programs