add: if (!this.grid) return null; 
context:     getGridBounds:function() {        var topLeftTile = this.grid[0][0];        var bottomRightTile = this.grid[this.grid.length-1][this.grid[0].length-1];        return new OpenLayers.Bounds(topLeftTile.bounds.left,                                      bottomRightTile.bounds.bottom,                                     bottomRightTile.bounds.right,                                      topLeftTile.bounds.top);    },
meta: 4411	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/4411/f5a3c16478333ce7bfa74ef24d62bc38ace13f4d/Grid.js/clean/lib/OpenLayers/Layer/Grid.js