the grid layer needs to clear its tile loading timeout when it's removed from the map, or moveGriddedTiles can be called with this.map set to null, r=crschmidt (closes #3110)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@11482 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

tests/Layer/Grid.html

@@ -593,7 +593,7 @@
 
     function test_Layer_Grid_destroy (t) {
 
-        t.plan( 7 );
+        t.plan( 8 );
 
         var map = new OpenLayers.Map('map');
         layer = new OpenLayers.Layer.Grid(name, url, params);
@@ -608,6 +608,7 @@
         map.addLayer(layer);
 
         map.setCenter(new OpenLayers.LonLat(0,0), 10);
+        map.setCenter(new OpenLayers.LonLat(1,1));
 
          
         //grab a reference to one of the tiles
@@ -616,6 +617,7 @@
 
         layer.destroy();
         t.eq( tile.imgDiv, null, "Tile destroyed" ); 
+        t.eq( layer.timerId, null, "Tile loading timeout cleared");
         
         t.ok( layer.grid == null, "tiles appropriately destroyed")