degesch: cleanup, fix no-tty mode FWIW

Removed the no color mode that couldn't even be enabled.

Not sure why we still support running without a proper terminal
but let's at least not make it crash for now.

degesch.c

@@ -1927,7 +1927,6 @@ struct completion_hook_vtable
 
 struct app_context
 {
-	bool no_colors;                     ///< Disable attribute printing
 	char *attrs_defaults[ATTR_COUNT];   ///< Default terminal attributes
 
 	// Configuration:
@@ -2620,16 +2619,17 @@ init_colors (struct app_context *ctx)
 	INIT_ATTR (JOIN,        g_terminal.color_set_fg[COLOR_GREEN]);
 	INIT_ATTR (PART,        g_terminal.color_set_fg[COLOR_RED]);
 
-	char *highlight = xstrdup_printf ("%s%s%s",
+	char *highlight = have_ti ? xstrdup_printf ("%s%s%s",
 		g_terminal.color_set_fg[COLOR_YELLOW],
 		g_terminal.color_set_bg[COLOR_MAGENTA],
-		enter_bold_mode);
+		enter_bold_mode) : NULL;
 	INIT_ATTR (HIGHLIGHT, highlight);
 	free (highlight);
 
 #undef INIT_ATTR
 
-	if (ctx->no_colors)
+	// This prevents formatters from obtaining an attribute printer function
+	if (!have_ti)
 	{
 		g_terminal.stdout_is_tty = false;
 		g_terminal.stderr_is_tty = false;
@@ -3749,7 +3749,7 @@ buffer_print_backlog (struct app_context *ctx, struct buffer *buffer)
 	int display_limit = MAX (10, g_terminal.lines - 1);
 
 	// Simulate curses-like fullscreen buffers if the terminal allows it
-	if (clear_screen)
+	if (g_terminal.initialized && clear_screen)
 	{
 		terminal_printer_fn printer = get_attribute_printer (stdout);
 		tputs (clear_screen, 1, printer);