Fix leaks of geany_run_script.

When an error occurred after geany_run_script was created the
script was not deleted (two places) and on an execute error it
would only be deleted if no working dir was specified.

These are the only places I can find. Should fix http://sourceforge.net/p/geany/bugs/975/ 
If nobody points out any other places it happens will commit in a few days.