fix: min connections cannot be less than 0

Author: manfredsteyer

frontend/src/app/coupling/graph/graph.component.html

@@ -8,7 +8,7 @@
 
   <mat-form-field appearance="outline" style="flex: 1">
     <mat-label>Min. Connections</mat-label>
-    <input type="number" matInput [formControl]="minConnectionsControl" />
+    <input type="number" matInput [formControl]="minConnectionsControl" min="0" />
   </mat-form-field>
 </div>