Allow GrowMask node to work with batches (for AnimateDiff) (#1623)

* Allow mask batches

This allows LatentCompositeMasked -node to work with AnimateDiff. I tried to keep old functionality too, unsure if it's correct, but both single mask and batch of masks seems to work with this change.

* Update nodes_mask.py

comfy_extras/nodes_mask.py

@@ -331,15 +331,14 @@ class GrowMask:
         out = []
         for m in mask:
             output = m.numpy()
-            while expand < 0:
+            for _ in range(abs(expand)):
+                if expand < 0:
                     output = scipy.ndimage.grey_erosion(output, footprint=kernel)
-                expand += 1
-            while expand > 0:
+                else:
                     output = scipy.ndimage.grey_dilation(output, footprint=kernel)
-                expand -= 1
             output = torch.from_numpy(output)
             out.append(output)
-        return (torch.cat(out, dim=0),)
+        return (torch.stack(out, dim=0),)