Crash when printing syntax trees

[Kaljurand]

$ ./ape.exe -text "John waits." -solo syntaxdpp
ERROR: type_error(atom,[]): atom_chars/2:

Also:

sh run.sh
APE> John waits.

ERROR: /home/kaarel/mywork/APE/runape.pl:190:
	atom_chars/2: Type error: `atom' expected, found `[]' (an empty_list)

The crash occurs at:

APE/utils/trees_to_ascii.pl

Line 102 in e2b06a9

atom_chars(Atom, AtomChars),

Possibly caused by the fact that [] is not an atom anymore (but is still atomic) in SWI-Prolog. Possible fix: replace the atomic check on line 100 with atom check.