Set terminus to undefined in period form if it doesn't have any values

Fixes #102

src/components/period_form/terminus_input.jsx

@@ -50,18 +50,28 @@ module.exports = React.createClass({
   },
 
   handleChangeAutoparsedLabel: function (e) {
-    var terminus = parse(e.target.value);
-    this.props.onChange(terminus);
-  },
+    var label = e.target.value;
+    this.props.onChange(label.length ? parse(label) : undefined);
+ },
 
   refreshAutoparse: function () {
     var terminus = parse(this.props.terminus.get('label'));
     this.props.onChange(terminus);
   },
 
   handleChange: function (field, e) {
-    var value = e.target.value;
-    this.props.onChange(this.props.terminus.setIn([].concat(field), value));
+    var { hasISOValue } = require('../../helpers/terminus')
+      , { terminus, onChange } = this.props
+      , value = e.target.value
+      , updatedTerminus = terminus.setIn([].concat(field), value)
+      , isEmpty
+
+    isEmpty = (
+      updatedTerminus.get('label').length === 0 &&
+      !hasISOValue(updatedTerminus)
+    )
+
+    onChange(isEmpty ? undefined : updatedTerminus);
   },
 
   render: function () {

src/tests/views.js

@@ -70,6 +70,21 @@ describe('Period form', function () {
     });
   });
 
+  it('Should have a null value for empty period termini', function () {
+    var view = makePeriodFormView()
+      , { startTerminus, stopTerminus } = view.refs.temporalCoverage.refs
+
+    Simulate.change(
+      React.findDOMNode(startTerminus).querySelector('[name="label"]'),
+      { target: { value: '1890'}});
+
+    Simulate.change(
+      React.findDOMNode(startTerminus).querySelector('[name="label"]'),
+      { target: { value: ''}});
+
+    assert.equal(view.getPeriodValue().get('start'), null);
+  });
+
   /*
   it('Should render errors', function () {
     var view = makePeriodFormView();