fix lumina embedding forward to not depend on weight dtype

Author: a-r-r-o-w

src/diffusers/models/embeddings.py

@@ -1787,7 +1787,7 @@ def __init__(self, hidden_size=4096, cross_attention_dim=2048, frequency_embeddi
     def forward(self, timestep, caption_feat, caption_mask):
         # timestep embedding:
         time_freq = self.time_proj(timestep)
-        time_embed = self.timestep_embedder(time_freq.to(dtype=self.timestep_embedder.linear_1.weight.dtype))
+        time_embed = self.timestep_embedder(time_freq.to(dtype=caption_feat.dtype))
 
         # caption condition embedding:
         caption_mask_float = caption_mask.float().unsqueeze(-1)