[Stable Diffusion] Hotfix (#299)

src/diffusers/schedulers/scheduling_pndm.py

@@ -110,7 +110,9 @@ class PNDMScheduler(SchedulerMixin, ConfigMixin):
             # produce better results. When using PNDM with `self.config.skip_prk_steps` the implementation
             # is based on crowsonkb's PLMS sampler implementation: https://github.com/CompVis/latent-diffusion/pull/51
             self.prk_timesteps = np.array([])
-            self.plms_timesteps = (self._timesteps[:-1] + self._timesteps[-2:-1] + self._timesteps[-1:])[::-1].copy()
+            self.plms_timesteps = np.concatenate([self._timesteps[:-1], self._timesteps[-2:-1], self._timesteps[-1:]])[
+                ::-1
+            ].copy()
         else:
             prk_timesteps = np.array(self._timesteps[-self.pndm_order :]).repeat(2) + np.tile(
                 np.array([0, self.config.num_train_timesteps // num_inference_steps // 2]), self.pndm_order