Fix useless assignment to local variable.

I don't understand this code, but I assume the assignment was meant to reset the property, not the local variable (which goes out of scope immediately afterwards).

Author: max-schaefer

src/search/FindBar.js

@@ -141,7 +141,7 @@ define(function (require, exports, module) {
             bars.forEach(function (bar) {
                 bar.close(true, false);
             });
-            bars = [];
+            FindBar._bars = [];
         }
     };