Double free in scan code

This is happening in Jim_Eval when we call "scan"

jimsh(26228,0x10c36c5c0) malloc: *** error for object 0x1093852a0: pointer being freed was not allocated
jimsh(26228,0x10c36c5c0) malloc: *** set a breakpoint in malloc_error_break to debug
[1]    26228 abort      ./test.tcl