Causes 'Sync Now' to appear in Firefox's Tools menu
If HTTPS Everywhere is installed and active, there is 'Sync Now' menu item visible in the 'Tools' menu, even though the Sync feature has not been set up (this is not supposed to happen). After clicking on 'Sync Now' or 'Set Up Sync...' and canceling the 'Sync Setup' dialog, 'Sync Now' disappears until the next restart.
Opening the 'Tools' menu causes this error to be logged:
Error: TypeError: popup is null Source File: chrome://https-everywhere/content/toolbar_button.js Line: 45
Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/15.0 Firefox/15.0a1