(fix) add minimal constraints when creating events or tasks

UI/Templates/SchedulerUI/UIxTaskEditorTemplate.wox

@@ -15,7 +15,8 @@
             <label><var:string label:value="Title"/></label>
             <input type="text"
                    class="md-title"
-                   ng-model="editor.component.summary"/>
+                   ng-model="editor.component.summary"
+                   required="required"/>
           </md-input-container>
           <md-button class="md-icon-button" ng-click="editor.cancel()">
             <md-icon aria-label="Close dialog">close</md-icon>
@@ -206,7 +207,8 @@
       <md-button type="button" ng-click="editor.component.$reset()">
         <var:string label:value="Reset"/>
       </md-button>
-      <md-button class="md-primary md-hue-3" type="submit">
+      <md-button class="md-primary md-hue-3" type="submit"
+                 ng-disabled="editor.eventForm.$invalid">
         <var:string label:value="Save"/>
       </md-button>
     </div>