Fix tabs overwriting cells during movement

When compiling ncurses with the `--enable-hard-tabs` option, it will
make use of tabs to speed up cursor movement. These tabs can be set at
positions which will overwrite existing characters.

Since these are only for movement and not supposed to write anything to
the terminal, it is now checked that a cell does not contain any
character before writing a tab to it.

This fixes #1933.

0 files changed, 0 insertions, 0 deletions