only initialize the current map

- issues#show would whod a double map otherwise (since the helper is called
  twice - once for show, once for the (hidden) form

Author: jkraemer

app/helpers/gtt_map_helper.rb

@@ -34,7 +34,7 @@ def map_tag(map: nil, layers: map&.layers,
       content_tag(:div, "", data: data, id: uid, class: 'ol-map'),
       javascript_tag("
         $(document).ready(function(){
-          $('div.ol-map').each(function(idx) {
+          $('##{uid}').each(function(idx) {
             App.init({
               target: this
             });