Bugfix: Fix -p flag when passing -s (#1022)

Author: WampyCakes

manim/scene/scene_file_writer.py

@@ -291,12 +291,11 @@ def save_final_image(self, image):
         image : np.array
             The pixel array of the image to save.
         """
-        file_path = self.image_file_path
         if not config["output_file"]:
-            file_path = add_version_before_extension(file_path)
+            self.image_file_path = add_version_before_extension(self.image_file_path)
 
-        image.save(file_path)
-        self.print_file_ready_message(file_path)
+        image.save(self.image_file_path)
+        self.print_file_ready_message(self.image_file_path)
 
     def idle_stream(self):
         """