ContactEdit: remove unset properties.

src/ContactEdit.tsx

@@ -283,8 +283,11 @@ class ContactEdit extends React.Component {
     )));
 
     function setProperty(name: string, value: string) {
+      comp.removeAllProperties(name);
+      if (value !== '') {
         comp.updatePropertyWithValue(name, value);
       }
+    }
 
     setProperty('org', this.state.org);
     setProperty('title', this.state.title);