enhance error handling

snippets/graph.html

@@ -9,7 +9,7 @@
 <link href="static/bulma-calendar/css/bulma-calendar.min.css" rel="stylesheet">
 <script src="static/bulma-calendar/js/bulma-calendar.min.js"></script>
 
-<div class="columns">
+<div class="columns" id="myselectors">
   <div class="column is-half">
     <div id="reportrange" style="background: #fff; cursor: pointer; padding: 5px 10px; border: 1px solid #ccc; width: 100%">
       <i class="fa fa-calendar"></i>&nbsp;
@@ -214,6 +214,7 @@ function drawGraph(deveui, alias, property, start, stop, create_graph) {
   </div>
 </article>`);
       } else if (mydata.msg.includes("error:")) {
+        $('#myselectors').hide();
         $('#chart').html(`<article class="message is-danger">
   <div class="message-body">
     Fehler im Aufruf