With this fix, running the following script does not crash Blender anymore.
import bpy
class CRASH_MT_pie_menu(bpy.types.Menu):
bl_label = "Crash Blender"
def draw(self, context):
layout = self.layout
pie = layout.menu_pie()
pie.prop_enum(context.scene.transform_orientation_slots[1], "type", value="GLOBAL")
bpy.utils.register_class(CRASH_MT_pie_menu)
bpy.ops.wm.call_menu_pie(name="CRASH_MT_pie_menu")