Make a default icon sized 20x20. If anyone can think of a better default size, feel free to change this.

git-svn-id: http://svn.openlayers.org/trunk/openlayers@454 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Icon.js

@@ -34,7 +34,7 @@ OpenLayers.Icon.prototype = {
     */
     initialize: function(url, size, offset, calculateOffset) {
         this.url = url;
-        this.size = size;
+        this.size = (size) ? size : new OpenLayers.Size(20,20);
         this.offset = (offset) ? offset : new OpenLayers.Pixel(0,0);
         this.calculateOffset = calculateOffset;