Refresh the SQL control, whenever necessary.

Also, remove the CodeMirror object for better clean up process.

When a SQL control/tab is rendered in a hidden element, it does not
render really well. Because - it rely on the height, and width of the
container to count the gutten position, and margin, and other elements.

Hence - whenever the tab, panel becomes visible, we will refresh the
control.

web/pgadmin/misc/sql/static/js/sql.js

@@ -78,6 +78,9 @@ function(_, $, pgBrowser) {
                 }
               });
             }
+          } else {
+            var e = pgAdmin.Browser.editor;
+            e.refresh.apply(e);
           }
           if (sql != '') {
             pgAdmin.Browser.editor.setValue(sql);