fix: MacOS MPS background can't handle large slices

per
- https://github.com/brycedrennan/imaginAIry/issues/175
- https://github.com/invoke-ai/InvokeAI/issues/1244

imaginairy/modules/attention.py

@@ -248,6 +248,11 @@ class CrossAttention(nn.Module):
             )
 
         slice_size = q.shape[1] // steps if (q.shape[1] % steps) == 0 else q.shape[1]
+        if get_device() == "mps":
+            # https://github.com/brycedrennan/imaginAIry/issues/175
+            # https://github.com/invoke-ai/InvokeAI/issues/1244
+            slice_size = min(slice_size, 2**30)
+
         for i in range(0, q.shape[1], slice_size):
             end = i + slice_size