feedback: skip wiping the prompt bar when the shortcut printed a message

When, at a prompt, the user chose a function shortcut instead of typing
an answer, and this function printed some message to the status bar,
then we do not want to wipe this message.  Also: the message overwrote
and cleared the prompt bar, so there is no need to wipe the latter.

This fixes https://savannah.gnu.org/bugs/?56273.

Bug existed since version 4.0, since justifying started giving feedback
(or rather since version 4.1, since M-J no longer crashed).

src/nano.c

@@ -2455,7 +2455,7 @@ int main(int argc, char **argv)
 		if (currmenu != MMAIN)
 			bottombars(MMAIN);
 
-		lastmessage = HUSH;
+		lastmessage = VACUUM;
 		as_an_at = TRUE;
 
 		/* Update the displayed current cursor position only when there

src/nano.h

@@ -147,7 +147,7 @@ typedef enum {
 } format_type;
 
 typedef enum {
-	HUSH, NOTICE, MILD, ALERT
+	VACUUM, HUSH, NOTICE, MILD, ALERT
 } message_type;
 
 typedef enum {

src/prompt.c

@@ -580,6 +580,8 @@ int do_prompt(bool allow_tabs, bool allow_files,
 	/* Reserve five columns for colon plus angles plus answer, ":<aa>". */
 	prompt[actual_x(prompt, (COLS < 5) ? 0 : COLS - 5)] = '\0';
 
+	lastmessage = VACUUM;
+
 	func = acquire_an_answer(&retval, allow_tabs, allow_files, &listed,
 								history_list, refresh_func);
 	free(prompt);
@@ -602,6 +604,7 @@ int do_prompt(bool allow_tabs, bool allow_files,
 	else if (func == do_enter)
 		retval = (*answer == '\0') ? -2 : 0;
 
+	if (lastmessage == VACUUM)
 		wipe_statusbar();
 
 #ifdef ENABLE_TABCOMP