Change check to crossattention

vit_gpt2/modeling_flax_gpt2.py

@@ -346,7 +346,7 @@ class FlaxGPT2Block(nn.Module):
         if encoder_hidden_states is not None:
 
             # add one self-attention block for cross-attention
-            if not hasattr(self, "cross_attn"):
+            if not hasattr(self, "crossattention"):
                 raise ValueError(
                     f"If `encoder_hidden_states` are passed, {self} has to be instantiated with "
                     "cross-attention layers by setting `config.add_cross_attention=True`"