The attached patch fixes a segmentation fault that occurs when a GDB 
script has an empty else clause.

E.g.

if $cond
   echo here\n
else
   # boom
end

The command structure is apparently read correctly (from the user's 
perspective), but GDB will crash when it tries to a) execute the else 
clause ($cond == 0), or b) free the command, if the command is not in a 
define or the user-defined command is redefined.

This problem is caused by a pointer that is only initialised when it is 
first used, which is never when there are no commands.

:ADDPATCH CLI:

Andrew Stubbs