Also apply for activated grids

Signed-off-by: phl0 <github@florian-wolters.de>

application/views/interface_assets/footer.php

@@ -1450,7 +1450,8 @@ $(document).ready(function(){
   var map = L.map('gridsquare_map', {
     layers: [layer],
     center: [19, 0],
-    zoom: 2
+    zoom: 2,
+    minZoom: 1
   });
 
   var grid_two = <?php echo $grid_2char; ?>;