core: always return nil on error
core: always return nil on error

We should always return a nil pointer of clusterInfo if
CreateOrLoadClusterInfo() returns an error.

Closes: https://github.com/rook/rook/issues/9314
Signed-off-by: Sébastien Han <62d754cc350e84d3b1c32ae79f976f5348e74a40@redhat.com>

rook/rook,rook/rook,rook/rook,rook/rook,rook/rook