Getting warning message in WordPress v4.7.3

Thank you very much for the nice help.

I am getting following warning message in WordPress v4.7.3:

Warning: Declaration of Walker_Nav_Menu_Edit_Custom::start_lvl(&$output) should be compatible with Walker_Nav_Menu::start_lvl(&$output, $depth = 0, $args = Array) in ~\wp-content\plugins\sweet-custom-menu\edit_custom_walker.php on line 219

Warning: Declaration of Walker_Nav_Menu_Edit_Custom::end_lvl(&$output) should be compatible with Walker_Nav_Menu::end_lvl(&$output, $depth = 0, $args = Array) in ~\wp-content\plugins\sweet-custom-menu\edit_custom_walker.php on line 219

Warning: Declaration of Walker_Nav_Menu_Edit_Custom::start_el(&$output, $item, $depth, $args) should be compatible with Walker_Nav_Menu::start_el(&$output, $item, $depth = 0, $args = Array, $id = 0) in ~\wp-content\plugins\sweet-custom-menu\edit_custom_walker.php on line 219

Warning: Declaration of rc_scm_walker::start_el(&$output, $item, $depth, $args) should be compatible with Walker_Nav_Menu::start_el(&$output, $item, $depth = 0, $args = Array, $id = 0) in ~\wp-content\plugins\sweet-custom-menu\custom_walker.php on line 48

Can you please check?

Best regards,
Kawsar