Set focus to the first focusable child of the cell

Closes #13327
(grafted from edd4d4ea6416280f2c03f3e6b87a9b62e6cc333c)

--HG--
branch : 7.0

sao/src/view/tree.js

@@ -1361,7 +1361,7 @@
                         if (this.editable && new_) {
                             td.trigger('click');
                         }
-                        td.find(':input,[tabindex=0]').focus();
+                        Sao.common.find_focusable_child(td).focus();
                     }
                 }
             };