[GRASS5] erase mon

[Maciek Sieczka]

grass57

when no monitor is started then pressing the "erase monitor" button in d.m
gives an error:

child process exited abnormally
child process exited abnormally
    while executing
"exec -- d.erase white >@ stdout 2>@ stderr"
    ("eval" body line 1)
    invoked from within
"eval exec -- $cmd $args >@ stdout 2>@ stderr"
    (procedure "run" line 2)
    invoked from within
"run $cmd "
    (procedure "Dm::erase" line 4)
    invoked from within
"Dm::erase"
    ("uplevel" body line 1)
    invoked from within
"uplevel \#0 $cmd"
    (procedure "Button::_release" line 18)
    invoked from within
"Button::_release .mainframe.topf.tb0.bbox1.b3"
    (command bound to event)