fixed a nasty bug related to capture of the controller version

fixed a nasty bug related to capture of the controller version caused by
the fact that it can only be captured when a site is selected

index.php

@@ -142,11 +142,12 @@
 }
 
 /*
-get the version of the controller (if not already stored in $_SESSION)
+get the version of the controller (if not already stored in $_SESSION or when empty)
 */
-if(!isset($_SESSION['detected_controller_version'])) {
+if(!isset($_SESSION['detected_controller_version']) || $_SESSION['detected_controller_version'] === '') {
     $site_info = $unifidata->stat_sysinfo();
-    $_SESSION['detected_controller_version'] = $site_info[0]->version;
+    $detected_controller_version = $site_info[0]->version;
+    $_SESSION['detected_controller_version'] = $detected_controller_version;
 }
 
 /*
@@ -515,7 +516,7 @@ function to print the output
         </div>
         <div class="row">
           <div class="col-sm-3 col-sm-offset-2">version detected</div>
-          <div class="col-sm-5"><span class="label label-primary"><?php echo $_SESSION['detected_controller_version'] ?></span></div>
+          <div class="col-sm-5"><span class="label label-primary"><?php echo $detected_controller_version ?></span></div>
         </div>
         <hr>
         <div class="row">