fix: pipeline none values (#649)

Author: ji-yaqi

google/cloud/aiplatform/utils/pipeline_utils.py

@@ -129,7 +129,7 @@ def _get_vertex_value(
           ValueError: if the parameter name is not found in pipeline root
           inputs, or value is none.
         """
-        if not value:
+        if value is None:
             raise ValueError("None values should be filterd out.")
 
         if name not in self._parameter_types: