Fix JS error. Bug 299873, patch by Henrik Skupin <hskupin@gmail.com>,

r=bsmedberg, a=asa

browser/base/content/baseMenuOverlay.xul

@@ -128,6 +128,7 @@
     </keyset>
 
     <stringbundleset id="stringbundleset">
+        <stringbundle id="bundle_browser" src="chrome://browser/locale/browser.properties"/>
         <stringbundle id="bundle_browser_region" src="chrome://browser-region/locale/region.properties"/>
     </stringbundleset>
 </overlay>