backport guard against executable location not set

__init__.py

@@ -3,7 +3,7 @@
 bl_info = {
     'name': 'Rhubarb Lipsync',
     'author': 'Andrew Charlton',
-    'version': (1, 0, 5),
+    'version': (1, 0, 6),
     'blender': (2, 79, 0),
     'location': 'Properties > Armature',
     'description': 'Integrate Rhubarb Lipsync into Blender',

op_blender_rhubarb.py

@@ -20,7 +20,9 @@ class RhubarbLipsyncOperator(bpy.types.Operator):
 
     @classmethod
     def poll(cls, context):
-        return context.selected_pose_bones and context.object.pose_library.mouth_shapes.sound_file
+        return context.preferences.addons[__package__].user_preferences.executable_path and \
+            context.selected_pose_bones and \
+            context.object.pose_library.mouth_shapes.sound_file
 
     def modal(self, context, event):
         try:

pnl_blender_rhubarb.py

@@ -44,6 +44,11 @@ def draw(self, context):
             row.prop(prop, 'start_frame', text='Start frame')
 
             row = layout.row()
+
+            if not (context.user_preferences.addons[__package__].preferences.executable_path):
+                row.label(text="Please set rhubarb executable location in addon preferences")
+                row = layout.row()
+
             row.operator(operator = "object.rhubarb_lipsync")
         else:
             row = layout.row(align=True)