Check if session description exists in edit dialog

Closes #412 (closed)

src/app/components/creator/_dialogs/room-edit/room-edit.component.html

@@ -5,14 +5,14 @@
     <mat-form-field class="input-block">
       <input [(ngModel)]="editRoom.name" matInput placeholder="{{ 'session.session-name' | translate}}"
              name="room-name" maxlength="20"/>
-      <mat-hint align="end">{{editRoom.name.length }} / 20</mat-hint>
+      <mat-hint align="end">{{ editRoom.name.length }} / 20</mat-hint>
     </mat-form-field>
     <mat-form-field class="input-block">
               <textarea [(ngModel)]="editRoom.description" matInput matTextareaAutosize
                         matAutosizeMinRows="2" matAutosizeMaxRows="5" maxlength="255"
                         placeholder="{{ 'session.description' | translate}}" name="description">
               </textarea>
-      <mat-hint align="end">{{editRoom.description.length }} / 255</mat-hint>
+      <mat-hint align="end">{{ editRoom.description ? editRoom.description.length : 0 }} / 255</mat-hint>
     </mat-form-field>
     <div fxLayoutAlign="center center">
       <button mat-raised-button class="delete" (click)="openDeleteRoomDialog()">