For kinetics databases, write reference and referenceType fields only if not None.

Author: connie

rmgpy/data/kinetics/common.py

@@ -203,10 +203,9 @@ def sortEfficiencies(efficiencies0):
         for line in lines[1:-1]:
             f.write('    {0}\n'.format(line))
         f.write('    ),\n'.format(lines[0]))
-    else:
-        f.write('    reference = None,\n')
 
-    f.write('    referenceType = "{0}",\n'.format(entry.referenceType))
+    if entry.referenceType != "":
+        f.write('    referenceType = "{0}",\n'.format(entry.referenceType))
     if entry.rank is not None:
         f.write('    rank = {0},\n'.format(entry.rank))
     f.write('    shortDesc = u"""')