[patch, fortran] Fix empty substrings when simplifying

[Thomas Koenig]

Am 24.03.2018 um 16:18 schrieb Jerry DeLisle:
> On 03/24/2018 05:46 AM, Thomas Koenig wrote:
>> Hell world,
>>
>> the attached patch is fairly self-explanatory, it fixes an out-of-memory
>> condition.
>>
>> Regression-tested. OK for trunk?
>>
> 
> Yes, and thanks for fix.

Committed as r258835, with Steve's observation of using
stop instead of call abort.

I, of all people, should know, but old habits die hard :-)

Regards

	Thomas