Only add a phrase if it is not None.

Author: F Saad

src/metamodels/cgpm_analyze/parse.py

@@ -88,7 +88,7 @@ def syntax_error(self, (token, text)):
 
     def p_anlaysis_start(self, ps):             self.phrases = ps
 
-    def p_phrases_one(self, p):                 return [p]
+    def p_phrases_one(self, p):                 return [p] if p else []
     def p_phrases_many(self, ps, p):
         if p: ps.append(p)
         return ps