Fix indexing bug in LazyEvaluatedKernelTensor (#1819)

Seems to have been a copy&paste error

Author: Balandat

gpytorch/lazy/lazy_evaluated_kernel_tensor.py

@@ -113,12 +113,12 @@ def _getitem(self, row_index, col_index, *batch_indices):
         # We're going to handle multi-batch indexing with a try-catch loop
         # This way - in the default case, we can avoid doing expansions of x1 which can be timely
         except IndexError:
-            if any([not isinstance(bi, slice) for bi in batch_indices]):
+            if any(not isinstance(bi, slice) for bi in batch_indices):
                 raise RuntimeError(
                     "Attempting to tensor index a non-batch matrix's batch dimensions. "
                     f"Got batch index {batch_indices} but my shape was {self.shape}"
                 )
-            x2 = x2.expand(*([1] * (len(batch_indices) - self.x1.dim() + 2)), *self.x2.shape)
+            x2 = x2.expand(*([1] * (len(batch_indices) - self.x2.dim() + 2)), *self.x2.shape)
             x2 = x2[(*batch_indices, col_index, dim_index)]
 
         if len(batch_indices) == 0 or all(ind == slice(None, None, None) for ind in batch_indices):