[FlaxStableDiffusionPipeline] fix bug when nsfw is detected (#832)

fix nsfw bug

src/diffusers/pipelines/stable_diffusion/pipeline_flax_stable_diffusion.py

@@ -291,6 +291,7 @@ class FlaxStableDiffusionPipeline(FlaxDiffusionPipeline):
             # block images
             if any(has_nsfw_concept):
                 for i, is_nsfw in enumerate(has_nsfw_concept):
+                    if is_nsfw:
                         images[i] = np.asarray(images_uint8_casted[i])
 
             images = images.reshape(num_devices, batch_size, height, width, 3)