Fix some console warning with the dashboard header

closes FALCOR-408

Test Plan:
  - Go to the dashboard
  - You shouldn't seen any warnings or errors in the
    console relating to invalid or missing props

Change-Id: I344a892ede66cb5f9f3ec62859642153bbfe80d1
Reviewed-on: https://gerrit.instructure.com/117609
Tested-by: Jenkins
Reviewed-by: Aaron Kc Hsu <ahsu@instructure.com>
QA-Review: Dan Sasaki <dsasaki@instructure.com>
Product-Review: Clay Diffrient <cdiffrient@instructure.com>

app/jsx/dashboard/DashboardHeader.js

@@ -78,10 +78,15 @@ class DashboardHeader extends React.Component {
 }
 
 DashboardHeader.propTypes = {
-  recent_activity_dashboard: bool.isRequired,
-  hide_dashcard_color_overlays: bool.isRequired,
+  recent_activity_dashboard: bool,
+  hide_dashcard_color_overlays: bool,
   planner_enabled: bool.isRequired,
   planner_selected: bool.isRequired
 }
 
+DashboardHeader.defaultProps = {
+  recent_activity_dashboard: false,
+  hide_dashcard_color_overlays: false
+}
+
 export default DashboardHeader;