Before the addition of multi-cursor support, we just returned the second
return value of the "replacer" function to the caller.
With the introduction of multi-cursors, we naively summed the second
return values for each cursor.
In some cases the "replacer" function doesn't return any second value,
so we tried to do math with `nil`, thus throwing errors.
Now the second return value is added to a table which is then returned
to the caller.
Guldoman
f92f56d42e