CVS griph: * fix segfault with expansion of $[n] when the argument string contains

[FVWM CVS]

CVSROOT:        /home/cvs/fvwm
Module name:    fvwm
Changes by:     griph   06/07/13 03:39:50

Modified files:
        .              : ChangeLog 
        fvwm           : expand.c 

Log message:
* fix segfault with expansion of $[n] when the argument string contains
no tokens.