Map.updateSize does not correctly check for the existence of layers

[tmcw]

In cases where a map is initialized and resized before adding layers (I'm running into that corner case somehow), I've found that the loop that calls onMapResize() on each layer doesn't check to see whether the map actually has any layers, and so OpenLayers fails on a null reference. Patch attached which addresses this issue by adding a condition that this.layers != null, like is asked elsewhere in the code.

[tmcw]

Add check for this.layers being null

[tschaub]

A different manifestation of this problem was ticketed in #2461. Can you please confirm that you are still seeing this issue after r10022. If so, please provide a test case that fails without this patch. We are piling a lot of workarounds in Map.js. Having well commented tests will help us remember what they are all about.

[tschaub]

This is further guarded against with r10044. Previously, the layers property of the map was initialized after calling map.updateSize. After r10044, this isn't the case.