Style improvement: use css from participant-room & bugfixing

src/app/creator-room/creator-room.component.html

 <div fxLayout="column" fxLayoutAlign="start" fxLayoutGap="20px" fxFill>
   <div fxLayout="row" fxLayoutAlign="center">
-
-    <mat-card>
+    <mat-card *ngIf="room">
       <mat-card-header>
         <mat-card-title><h3 class="subheading-2">{{ room.name }}</h3></mat-card-title>
         <mat-card-subtitle>{{ room.id }}</mat-card-subtitle>
@@ -26,10 +25,11 @@
         <button mat-button color="warn" matTooltip="Delete selected room">
           Delete room
         </button>
-        <button mat-button color="primary" matTooltip="Go back to last page">
+        <button mat-button color="primary" matTooltip="Go back to last page" (click)="goBack()">
           Go back
         </button>
       </mat-card-actions>
     </mat-card>
+    <div *ngIf="!isLoading && !room">Error</div>
   </div>
 </div>

src/app/creator-room/creator-room.component.scss

+mat-card {
+  max-width: 800px;
+}
+
+mat-card-content > :first-child {
+  margin-top: 16px;
+}