Fix event editing.

It was crashing due to 7917b1fbe1.

src/components/EventEdit.tsx

@@ -63,6 +63,7 @@ class EventEdit extends React.PureComponent {
     };
 
     const locState = this.props.location.state;
+    if (locState) {
       // FIXME: Hack to determine if all day. Should be passed as a proper state.
       this.state.allDay = (locState.start &&
         (locState.start.getHours() === 0) &&
@@ -71,6 +72,7 @@ class EventEdit extends React.PureComponent {
         (locState.start.getMinutes() === locState.end.getMinutes()));
       this.state.start = (locState.start) ? locState.start : undefined;
       this.state.end = (locState.end) ? locState.end : undefined;
+    }
 
     if (this.props.item !== undefined) {
       const event = this.props.item;