Fix AttributeError in editor surname tab

When using arrow up/down keys, curr_path isn't set, so when attempting
to delete the surname, an AttributeError exception is thrown. This is
avoided by initalizing curr_path.

Fixes #13322

Author: hgohel

gramps/gui/editors/displaytabs/surnametab.py

@@ -98,6 +98,7 @@ def __init__(
         self.curr_col = -1
         self.curr_cellr = None
         self.curr_celle = None
+        self.curr_path = None
 
         EmbeddedList.__init__(
             self,