having "Description: Too few items in renditions." when compiling

I have the error:

.../Assets.xcassets: error: Multiple validation errors occurred.
    Underlying Errors:
        Description: Too few items in renditions.
        Description: Too few items in renditions.
        Description: Too few items in renditions.
        Description: Too few items in renditions.
        Description: Too few items in renditions.

when trying to compile in Xcode

Any suggestion about how to fix it?