Исправление.

table.gd:358 @ remove_row(): Condition "p_child->data.parent != this" is true.
    <Исходный код C++>scene/main/node.cpp:1419 @ remove_child()
    <Трассировка стека>table.gd:358 @ remove_row()
    frm_threats.gd:35 @ _on_btn_del_thr_pressed()

table/table.gd

@@ -355,7 +355,7 @@ func remove_row(i_row: int):
         var selector = nodes[sel_key]
         var node_key: String = get_node_key(NODE_KEY_FORMAT, 0, i_row)
         var node = nodes[node_key]
-        node.get_parent().remove_child(selector)
+        node.remove_child(selector)
         selector.queue_free()
         nodes.erase(sel_key)
     for i_col in columns: