FcCharSetPutLeaf(): Fix missing move of new_leaves contents
If the realloc(numbers) call fails, shrinking the leaves allocation
back to the old size is not guaranteed to return the old pointer value.
While this might be the case with some malloc() implementations, realloc()
could also just mark the following area as free.
To make this less error-prone, we grow numbers first and then grow leaves
since the numbers content does not need to be relocated, but leaves does.