Do not fail when only one positional argument is after labeled ones
This is actually safe, as demonstrated by the property introduced in this commit; the intuition for it is that we re-order arguments by swapping their positions. So if only one positional argument comes after all the labeled one, it will necessarily end up in the correct positions after all the labeled ones have been placed in their position. Fixes #1164. Signed-off-by: KtorZ <[email protected]>