Added test case for null string

Added fix to check to see if __iter__ was not a string, which was causing a failure

python/lsst/daf/base/baseLib.i

@@ -208,7 +208,7 @@ def _guessIntegerType(container, name, value):
 
 def _propertyContainerSet(container, name, value, typeMenu, *args):
     """Set a single Python value of unknown type"""
-    if hasattr(value, "__iter__"):
+    if hasattr(value, "__iter__") and not isinstance(value, str):
         exemplar = value[0]
     else:
         exemplar = value

tests/PropertySet_2.py

@@ -48,6 +48,7 @@ def testScalar(self):
         ps.setString("string", "bar")
         ps.set("int2", 2009)
         ps.set("dt", dafBase.DateTime("20090402T072639.314159265Z"))
+        ps.set("blank", "")
 
         self.assertEqual(ps.typeOf("bool"), dafBase.PropertySet.TYPE_Bool)
         self.assertEqual(ps.getBool("bool"), True)
@@ -71,6 +72,7 @@ def testScalar(self):
         self.assertEqual(ps.get("int2"), 2009)
         self.assertEqual(ps.typeOf("dt"), dafBase.PropertySet.TYPE_DateTime)
         self.assertEqual(ps.getDateTime("dt").nsecs(), long(1238657233314159265))
+        self.assertEqual(ps.getString("blank"), "")
 
     def testNumPyScalars(self):
         """Test that we can also pass NumPy array scalars to PropertySet setters.