fixed a bug in add_error

during parsing ('sin'), it was causing a crash when creating the error message

Author: jacobwilliams

src/function_parser.f90

@@ -1471,7 +1471,7 @@ subroutine add_error (me, j, ipos, funcstr, msg)
 
     call me%error_msg%add(' '//trim(funcstr))
 
-    tmp = repeat(' ',ipos(j))//'?'     ! Advance to the jth position
+    tmp = repeat(' ',ipos(min(j,size(ipos))))//'?'     ! Advance to the jth position
     call me%error_msg%add(tmp)
     deallocate(tmp)