Handle default fonts when setting vmem.

src/conio/bitmap_con.c

@@ -302,6 +302,8 @@ static void set_vmem_cell(struct vstat_vmem *vmem_ptr, size_t pos, uint16_t cell
 	if (!vstat.blink_altcharset)
 		altfont &= ~0x02;
 	font=current_font[altfont];
+	if (font == -99)
+		font = default_font;
 	if (font < 0 || font > 255)
 		font = 0;