Please update both to WPML (4.5.12) and String Translation (3.2.3). (If necessary, from the commercial tab of the Add New plugins page—which takes you to the custom WPML installer—click Check for Updates to see the current versions).
If you cannot access the site because of the fatal error, you may need to use FTP to change the String Translation plugin folder name, which will deactivate it (see hidden link). You can then delete it from the plugins page and reinstall it (with the latest version).
the footer widgets disappeaed now.... I can see the widget in the string translator but please let me know how we can add these again in the widget blocks based on the existing string translator