No longer allow the customer view screen to be closed outside of application exit.

QueueSys/frmCustomerView.cs

@@ -43,5 +43,10 @@ namespace QueueSys
         {
             RefreshCustomerView();
         }
+
+        private void frmCustomerView_FormClosing(object sender, FormClosingEventArgs e)
+        {
+            e.Cancel = true;
+        }
     }
 }