MNT: more codeql warnings addressed

Author: tacaswell

Diff for: mpl_gui/__init__.py

@@ -235,7 +235,7 @@ def show_all(self, *, block=None, timeout=None):
         if timeout is None:
             timeout = self._timeout
         self._ensure_all_figures_promoted()
-        show(self.figures, block=self._block, timeout=self._timeout)
+        show(self.figures, block=self._block, timeout=timeout)
 
     # alias to easy pyplot compatibility
     show = show_all
@@ -312,6 +312,7 @@ def close(self, val):
             _FigureCanvasBase(figure=fig)
         assert fig.canvas.manager is None
         self._fig_to_number.pop(fig, None)
+        return
 
 
 class FigureContext(FigureRegistry):