Show hidden map if it's requested by URL wtracks?map=...

It is only shown transiently:
* since right now map is remembered, it will still be shown on next refresh (could be changed)
* but as soon as user changes it, it will be hidden again

js/wtracks.js

@@ -2059,8 +2059,10 @@ $(function(){
   // Add maps and overlays
   var baseLayers = {};
   var overlays = {};
+  var baseLayer = getVal("wt.baseLayer", config.display.map);
+  var requested_map = getParameterByName('map')
   mapsForEach(function(name, props) {
-    if (props.on) {
+    if (props.on || name === requested_map || name == baseLayer) {
       var inList = props.in == MAP_MY ? mymaps : config.maps;
       var tile = getProvider(inList[name]);
       if (tile) {
@@ -2080,7 +2082,6 @@ $(function(){
 
   // ----------------------
 
-  var baseLayer = getVal("wt.baseLayer", config.display.map);
   var initialLayer = baseLayers[baseLayer] || baseLayers[config.display.map];
   if (!initialLayer) {
     //var availableLayerNames = "";