Fix size of preallocated array
Commit 084e1d86 added a preallocation to an array to avoid reallocations later on, but neglected the fact that after N insertions into the array, there’s always a NULL terminator added to the end. Fix the preallocation to include that NULL terminator.
This doesn’t change the correctness of the code, but should eliminate one reallocation.
Spotted by Sebastian Dröge. See glib!674 (merged).
Signed-off-by: Philip Withnall withnall@endlessm.com