ncurses: cosmetics

Remove braces around a single statement
Merge some comparisons
"( a )"             -> "(a)"
"if(x)"             -> "if (x)"
"if (x == NULL)"    -> "if (!x)"
"if (x != NULL)"    -> "if (x)"

ReadDir: Invert logic to have less indentation:
{
    if( a )
        x();
    else
        y();
}
====>
{
    if( !a )
    {
        y();
        return;
    }

    x();
}