Merge pull request #1084 from cdavis5e/fix-1064-2

MVKCmdCopyImage: Fix another copy-pasto.
diff --git a/MoltenVK/MoltenVK/Commands/MVKCmdTransfer.mm b/MoltenVK/MoltenVK/Commands/MVKCmdTransfer.mm
index 5986ecf..00e79dc 100644
--- a/MoltenVK/MoltenVK/Commands/MVKCmdTransfer.mm
+++ b/MoltenVK/MoltenVK/Commands/MVKCmdTransfer.mm
@@ -158,7 +158,7 @@
             VkExtent3D srcExtent = _srcImage->getExtent3D(srcPlaneIndex, srcLevel);
             uint32_t dstLevel = vkIC.dstSubresource.mipLevel;
             uint32_t dstBaseLayer = vkIC.dstSubresource.baseArrayLayer;
-            VkExtent3D dstExtent = _dstImage->getExtent3D(srcPlaneIndex, dstLevel);
+            VkExtent3D dstExtent = _dstImage->getExtent3D(dstPlaneIndex, dstLevel);
             // If the extent completely covers both images, I can copy all layers at once.
             // This will obviously not apply to copies between a 3D and 2D image.
             if (mvkVkExtent3DsAreEqual(srcExtent, vkIC.extent) && mvkVkExtent3DsAreEqual(dstExtent, vkIC.extent)) {