Merge pull request matplotlib#30326 from meeseeksmachine/auto-backport-of-pr-30321-on-v3.10.x

Backport PR matplotlib#30321 on branch v3.10.x (Fix type annotation for Axes.get_legend() to include None)

Author: dstansby

lib/matplotlib/axes/_base.pyi

@@ -224,7 +224,7 @@ class _AxesBase(martist.Artist):
         ymin: float | None = ...,
         ymax: float | None = ...
     ) -> tuple[float, float, float, float]: ...
-    def get_legend(self) -> Legend: ...
+    def get_legend(self) -> Legend | None: ...
     def get_images(self) -> list[AxesImage]: ...
     def get_lines(self) -> list[Line2D]: ...
     def get_xaxis(self) -> XAxis: ...