Declare elementBoundRect as var

Fixes #225

Author: nigelmegitt

src/main/js/html.js

@@ -708,7 +708,7 @@
                 if (se === ee) {
 
                     // Check to see if there's any background at all
-                    elementBoundingRect = se.node.getBoundingClientRect();
+                    var elementBoundingRect = se.node.getBoundingClientRect();
 
                     if (elementBoundingRect.width == 0 || elementBoundingRect.height == 0) {