Fix add_action for NER, so labelled 'O' actions aren't added

spacy/syntax/ner.pyx

@@ -220,6 +220,31 @@ cdef class BiluoPushDown(TransitionSystem):
             raise Exception(move)
         return t
 
+    def add_action(self, int action, label_name):
+        cdef attr_t label_id
+        if not isinstance(label_name, (int, long)):
+            label_id = self.strings.add(label_name)
+        else:
+            label_id = label_name
+        if action == OUT and label_id != 0:
+            return
+        if action == MISSING or action == ISNT:
+            return
+        # Check we're not creating a move we already have, so that this is
+        # idempotent
+        for trans in self.c[:self.n_moves]:
+            if trans.move == action and trans.label == label_id:
+                return 0
+        if self.n_moves >= self._size:
+            self._size *= 2
+            self.c = <Transition*>self.mem.realloc(self.c, self._size * sizeof(self.c[0]))
+        self.c[self.n_moves] = self.init_transition(self.n_moves, action, label_id)
+        assert self.c[self.n_moves].label == label_id
+        self.n_moves += 1
+        return 1
+
+
+
     cdef int initialize_state(self, StateC* st) nogil:
         # This is especially necessary when we use limited training data.
         for i in range(st.length):