Fix incomplete error printing

[djrieger]

Parser/lexer errors currently look like this:

arser error at line 5, column 7: parsing "int": 
      int a = 3;
      ^

while semantic errors don't get truncated:

Semantic error at line 2, column 26: Type String of parameter a undeclared.
    public static void main(String[] a) {}

[Nidan]

fixed in 2d76049