Error handling with duplicate tree families #45
Description
When a tulipac grammar contains the same tree family name twice, Alto throws an incomprehensible error.
Reading grammar from simpleG.tag ...
Exception in thread "main" java.lang.NullPointerException
at de.up.ling.irtg.codec.TulipacInputCodec.buildWordByItself(TulipacInputCodec.java:170)
at de.up.ling.irtg.codec.TulipacInputCodec.buildGrmr(TulipacInputCodec.java:79)
at de.up.ling.irtg.codec.TulipacInputCodec.parseFile(TulipacInputCodec.java:62)
at de.up.ling.irtg.codec.TulipacInputCodec.read(TulipacInputCodec.java:51)
at de.up.ling.irtg.codec.TulipacInputCodec.read(TulipacInputCodec.java:43)
at de.up.ling.irtg.script.TulipacParser.reloadGrammar(TulipacParser.java:60)
at de.up.ling.irtg.script.TulipacParser.main(TulipacParser.java:181)