Fix blinking/bold text in terminals with no color support

Before this, doing "TERM=vt100 irssi" showed all text as bold and blinking because of a failed check of window->term->TI_colors that was doing (value & 8) and not expecting a value of 0.

The changed lines themselves look a bit weird, but they make more sense in the context of the original commit, 96a292d4 (@ailin-nemui, requesting opinion)