MDL-46480 fix get_htmlelement_size() to deal with hidden or non-block elements

lib/javascript-static.js

@@ -332,7 +332,11 @@ M.util.init_maximised_embed = function(Y, id) {
             if (val == 'auto') {
                 val = el.getComputedStyle(prop);
             }
-            return parseInt(val);
+            val = parseInt(val);
+            if (isNaN(val)) {
+                return 0;
+            }
+            return val;
         } else {
             return 0;
         }