del editabletree_entry on remove-widget instead of quit_cell

issue3245
review918002
(transplanted from bc89814018e620da9d507688c1ba7047addcc39b)

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extra : transplant_source : %BC%89%81%40%18%E6%20%DA%9DPv%88%C1%BApG%AD%DC%C3%9B