better bool conditions when poping pages by index and always pop by index

Signed-off-by: Matej Starc <matej.starc@protonmail.com>

- do not pop pages if provided index is not at least by 2 smaller than the item count because it won't remove any pages unless it is.
- always pop pages by index. This makes it less error-prone because of the checks the columnview::pop(int) has.