Fix event editing.

It was crashing due to 7917b1fbe1.

src/components/EventEdit.tsx

@@ -63,14 +63,16 @@ class EventEdit extends React.PureComponent {
     };
 
     const locState = this.props.location.state;
-    // FIXME: Hack to determine if all day. Should be passed as a proper state.
-    this.state.allDay = (locState.start &&
-      (locState.start.getHours() === 0) &&
-      (locState.start.getMinutes() === 0) &&
-      (locState.start.getHours() === locState.end.getHours()) &&
-      (locState.start.getMinutes() === locState.end.getMinutes()));
-    this.state.start = (locState.start) ? locState.start : undefined;
-    this.state.end = (locState.end) ? locState.end : undefined;
+    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) &&
+        (locState.start.getMinutes() === 0) &&
+        (locState.start.getHours() === locState.end.getHours()) &&
+        (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;