OPC-UA extension ui Application URI made optional

ui/src/app/extension/extensions-forms/extension-form-opc.tpl.html

@@ -63,10 +63,7 @@
 
                                             <md-input-container flex="50" class="md-block" md-is-error="theForm['applicationUri_' + serverIndex].$touched && theForm['applicationUri_' + serverIndex].$invalid">
                                                 <label translate>extension.opc-application-uri</label>
-                                                <input required name="applicationUri_{{serverIndex}}" ng-model="server.applicationUri">
-                                                <div ng-messages="theForm['applicationUri_' + serverIndex].$error">
-                                                    <div translate ng-message="required">extension.field-required</div>
-                                                </div>
+                                                <input name="applicationUri_{{serverIndex}}" ng-model="server.applicationUri">
                                             </md-input-container>
                                         </div>