gmoccapy_1_3_5_1 - forgot to reset the gcode error string

ver. 1.3.5.1
- forgot to reset the gcode error, resulting in showing it only once,
  it was not shown again if a good file was loaded and than again the
  wrong one, now the load and edit button do reset the error code.


Signed-off-by: Norbert Schechner <nieson@web.de>
Merge branch '2.6' of ssh://norbert@git.linuxcnc.org/git/linuxcnc.git into 2.6