Fix random menu/display file selection when some files can't be displayed

When one or more files that match the menu file pattern can't be displayed
(e.g. the user's terminal is not wide enough or there's any other menu file
open/read error), pick another random menu file and try displaying that one,
until either a menu file has been displayed successfully or all files
(matching the pattern) have been attempted.

For example, you have text/menu/random1.c80.msg and random2.msg, if the first
file (random1.c80.msg) is selected at random but the user's terminal isn't
at least 80 columns wide, another file will be picked at random. Since only
random2.msg remains in the list (matching the pattern "random*"), that's the
only file that will always be displayed.

src/sbbs3/prntfile.cpp

@@ -388,11 +388,15 @@ bool sbbs_t::random_menu(const char *name, int mode, JSObject* obj)
 	strListDedupe(&names, /* case_sensitive: */ true);
 	bool   result = false;
 	size_t count = strListCount(names);
-	if (count > 0) {
+	while (count > 0) {
 		size_t i = sbbs_random(count);
 		if (menu_exists(names[i], NULL, path)) {
 			result = menu(names[i], mode, obj);
+			if (result == true)
+				break;
 		}
+		strListFastDelete(names, i, 1);
+		--count;
 	}
 	strListFree(&names);
 	return result;