Fix FluxIPAdapterTesterMixin (huggingface#10354)

Author: hlky

src/diffusers/loaders/transformer_flux.py

@@ -177,3 +177,5 @@ def _load_ip_adapter_weights(self, state_dicts, low_cpu_mem_usage=False):
 
         self.encoder_hid_proj = MultiIPAdapterImageProjection(image_projection_layers)
         self.config.encoder_hid_dim_type = "ip_image_proj"
+
+        self.to(dtype=self.dtype, device=self.device)