Add try/catch around error-throwing service calls.

guacamole/src/main/webapp/scripts/admin-ui.js

@@ -545,11 +545,21 @@ GuacAdmin.addUser = function(name) {
                 // Delete user upon confirmation
                 if (confirm("Are you sure you want to delete the user \""
                             + name + "\"?")) {
+
+                    // Attempt to delete user
+                    try {
                         GuacamoleService.Users.remove(GuacAdmin.selected_user);
                         deselect();
                         GuacAdmin.reset();
                     }
 
+                    // Alert on failure
+                    catch (e) {
+                        alert(e.message);
+                    }
+
+                }
+
             };
 
         }
@@ -815,11 +825,21 @@ GuacAdmin.addConnection = function(connection) {
                 // Delete connection upon confirmation
                 if (confirm("Are you sure you want to delete the connection \""
                             + connection.id + "\"?")) {
+
+                    // Attempt to delete connection
+                    try {
                         GuacamoleService.Connections.remove(GuacAdmin.selected_connection);
                         deselect();
                         GuacAdmin.reset();
                     }
 
+                    // Alert on failure
+                    catch (e) {
+                        alert(e.message);
+                    }
+
+                }
+
             };
 
         }