Cormen RB-DELETE_FIXUP(T,x) when x has no siblings
Let $x$ denote the node you want to delete and $p(x)$ its parent. If $x$ has no sibling, then it necessarily means that $x$ is a red node, otherwise two path from $p(x)$ could have a different number of black nodes (therefore the tree is not a Red-black tree).
So the situation where $x$ is black and has no sibling can never happen (and the tree in your example is not a Red-black tree).