Clear saved lsmask is new lsmask is passed

Author: nparley

lib/mpl_toolkits/basemap/__init__.py

@@ -3901,6 +3901,9 @@ def drawlsmask(self,land_color="0.8",ocean_color="w",lsmask=None,
         # look for axes instance (as keyword, an instance variable
         # or from plt.gca().
         ax = kwargs.pop('ax', None) or self._check_ax()
+        # Clear saved lsmask is new lsmask is passed
+        if lsmask is not None or lsmask_lons is not None or lsmask_lats is not None:
+            self.lsmask = None
         # if lsmask,lsmask_lons,lsmask_lats keywords not given,
         # read default land-sea mask in from file.
         if lsmask is None or lsmask_lons is None or lsmask_lats is None: