fix: (sticky | subheader) - fix little bug on refreshElements()

src/components/sticky/sticky.js

@@ -126,7 +126,7 @@ function MdSticky($document, $mdEffects, $compile, $$rAF, $mdUtil) {
       // be the same as their order of display.
       self.items.forEach(refreshPosition);
       self.items = self.items.sort(function(a, b) {
-        return a.top > b.top;
+        return a.top - b.top;
       });
 
       // Find which item in the list should be active,