Use handle.get_array to get mappable information

Due to inconsistencies in the colormap setup, it is suggested to instead
check for `get_array` to get an array of values to be color mapped. This
check is more robust irrespective of whatever the type of colormap is
set to be.

Author: chahak13

lib/matplotlib/legend.py

@@ -563,7 +563,7 @@ def val_or_rc(val, rc_name):
             getter_names = color_getters[labelcolor]
             for handle, text in zip(self.legendHandles, self.texts):
                 try:
-                    if isinstance(handle.cmap, colors.LinearSegmentedColormap):
+                    if handle.get_array() is not None:
                         continue
                 except AttributeError:
                     pass