[BUG] gu and gd fail if a wrap highlighter isn't enabled and "destination" character isn't visible

### Version of Kakoune Commit 024c17d0cad796aa42f7f08a73e09c3b7a438bfa (current master) ### Reproducer Open kakoune (with `kak -n`) in a narrow terminal window (I tested with 25 columns). Get the following text in the buffer, e.g by copying and pasting it in insert mode: ``` aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa b aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa b aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa b aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa b aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa b aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa b ``` Place the cursor on the `b` that's shown like `[b]`: ``` aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa b aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa b aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa b aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa [b] aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa b aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa b ``` Press `gu`. See how the cursor goes to the top of the buffer. The same happens if you go to the last `b` of the first chunk and press `gd`. ### Outcome The cursor goes to the top of the buffer (first character). ### Expectations `gu` and `gd` should act like `j` and `k` when there is no wrap highlighter. Both should have moved the cursor to the empty line. ### Additional information _No response_