Empty specs accepted by matcher.add_pattern, but cause error

[honnibal]

From Issue #429:

import spacy
import spacy.matcher

nlp = spacy.load('en', parser=False, entity=False)
matcher = spacy.matcher.Matcher(nlp.vocab)
content = u'''a b; c'''
matcher.add(entity_key='1', label='TEST', attrs={}, specs=[[]])
matcher(nlp(content))
->

Traceback (most recent call last): 
  File "word2vec/matcher_bla.py", line 8, in <module>
    matcher(nlp(content))
  File "spacy/matcher.pyx", line 315, in spacy.matcher.Matcher.__call__ (spacy/matcher.cpp:8519)
Exception: Error selecting action in matcher

Caused by empty specs. While I understand that this is a mistake in my data it's better to check this when entity is being added.

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.