Change time picker tooltip if there is no time filter

src/app/panels/timepicker/module.html

@@ -15,7 +15,7 @@
     <ul class="nav nav-pills timepicker-dropdown">
       <li class="dropdown">
 
-        <a class="dropdown-toggle timepicker-dropdown" data-toggle="dropdown" href="" bs-tooltip="(time.from.date | date:'yyyy-MM-dd HH:mm:ss.sss') + ' <br>to<br>' +(time.to.date | date:'yyyy-MM-dd HH:mm:ss.sss')" data-placement="bottom" ng-click="dismiss();">
+        <a class="dropdown-toggle timepicker-dropdown" data-toggle="dropdown" href="" bs-tooltip="time.from.date ? (time.from.date | date:'yyyy-MM-dd HH:mm:ss.sss') + ' <br>to<br>' +(time.to.date | date:'yyyy-MM-dd HH:mm:ss.sss') : 'Click to set a time filter'" data-placement="bottom" ng-click="dismiss();">
 
           <span ng-show="filterSrv.idsByType('time').length">
             <span class="pointer" ng-hide="panel.now">{{time.from.date | date:'MMM d, y HH:mm:ss'}}</span>
@@ -24,7 +24,7 @@
             <span class="pointer" ng-hide="panel.now" >{{time.to.date | date:'MMM d, y HH:mm:ss'}}</span>
             <span class="pointer" ng-show="panel.now">{{time.to.date | moment:'ago'}}</span>
           </span>
-          <span ng-hide="filterSrv.idsByType('time').length">Set a time filter</span>
+          <span ng-hide="filterSrv.idsByType('time').length">Time filter</span>
           <span ng-show="dashboard.current.refresh" class="text-warning">refreshed every {{dashboard.current.refresh}} </span>
           <i class="icon-caret-down"></i>
         </a>