Display an error if home path is not valid for a subvolume

src/include/users/dialogs.rb

@@ -1370,6 +1370,7 @@ def EditUserDialog(what)
             no_skel = Convert.to_boolean(UI.QueryWidget(Id(:skel), :Value))
             mode = Convert.to_string(UI.QueryWidget(Id(:mode), :Value))
           end
+
           if Ops.add(Builtins.findlastof(new_home, "/"), 1) ==
               Builtins.size(new_home)
             new_home = Builtins.substring(
@@ -1379,6 +1380,17 @@ def EditUserDialog(what)
             )
           end
 
+          # Check if is a valid path when creating a Btfs subvolume
+          if btrfs_subvolume && !valid_btrfs_path?(new_home)
+            Report.Error(
+              _("Given path is not a valid Btrfs location.\n\n" \
+              "Choose another path for the home directory\n" \
+              "or uncheck the 'Btrfs subvolume' option.")
+            )
+            focus_tab.call(current, :home)
+            next
+          end
+
           if do_not_edit
             new_home = home
             new_shell = shell