Deleting a region flag also deletes group flag

The group flags set with /region flag -g have no effect if the
normal flag is not also set, nor will they be displayed with
/region info once the normal flag is deleted. However, if a
group flag was to remain set in the database, the next time a
user sets the normal flag, they might be surprised to suddenly
see the corresponding group set as well.

Since the -g group is presented to the user as an attribute of
the normal flag, rather than a standalone flag, the group flag
should be deleted along with the normal flag.

src/main/java/com/sk89q/worldguard/bukkit/commands/RegionCommands.java

@@ -798,6 +798,12 @@ public void flag(CommandContext args, CommandSender sender) throws CommandExcept
             // Clear the flag only if neither [value] nor [-g group] was given
             region.setFlag(foundFlag, null);
 
+            // Also clear the associated group flag if one exists
+            RegionGroupFlag groupFlag = foundFlag.getRegionGroupFlag();
+            if (groupFlag != null) {
+                region.setFlag(groupFlag, null);
+            }
+
             sender.sendMessage(ChatColor.YELLOW
                     + "Region flag '" + foundFlag.getName() + "' cleared.");
         }