Avoid dangerous default value

scripts/wk/ui/tui.py

@@ -227,9 +227,10 @@ class TUI():
       self,
       line1: str = 'Title Text',
       line2: str = '',
-      colors: list[str] | None = ['BLUE', ''],
+      colors: list[str] | None = None,
       ) -> None:
     """Remove all extra title panes, reset main title pane, and update layout."""
+    colors = self.title_colors if colors is None else colors
     panes = self.layout['Title']['Panes'].copy()
     if len(panes) > 1:
       tmux.kill_pane(*panes[1:])