If find is set to print files that are newer than a reference file and this
reference file is not specified (-newerXY), find crashes with a segmentation
fault. This is caused by incrementing the argument pointer arg_ptr without a
bounds check (parser.c:1315) resulting in a null pointer dereference
(lib/quotearg.c:249).

Examples of Correct Fixes:
Check for nullpointer directly after increment of arg ptr. 

Examples of Incorrect Fixes: 
1) Check for nullpointer only before or in fatal_file_error (Incomplete Fix
because null pointer might still propagate via parser.c:1342 or parser.c:1347). 

2) Do not increment the pointer at all (Regression because some arguments may
not be parsed, at all).
