Don't try to create invalid `BatchedDot` in `specialize_matmul_to_batched_dot` rewrite

pytensor/tensor/rewriting/blas.py

@@ -916,6 +916,10 @@ def specialize_matmul_to_batched_dot(fgraph, node):
     """
     x, y = node.inputs
 
+    if x.type.ndim < 3:
+        # This doesn't actually have a batch dimension
+        return None
+
     # BatchedDot does not allow implicit broadcasting of the batch dimensions
     # We do not want to explicitly broadcast as it may result in huge arrays
     if x.type.broadcastable[:-2] != y.type.broadcastable[:-2]:
@@ -926,6 +930,7 @@ def specialize_matmul_to_batched_dot(fgraph, node):
     if len(x_shape) > 3:
         # If we have more than one batch dim, ravel it
         x = x.reshape((-1, x_shape[-2], x_shape[-1]))
+    if len(y_shape) > 3:
         y = y.reshape((-1, y_shape[-2], y_shape[-1]))
 
     new_out = _batched_dot(x, y)