Add subject deletion that doesn't work

src/edit-subject-dialog.vala

@@ -101,9 +101,8 @@ public class EditSubjectDialog : Adw.Window {
                         case "0":
                             break;
                         case "1":
-                            subject = null;
-			                accept = true;
-                            this.close ();
+                            subject.deleted = true;
+                            close ();
                             break;
                         }
                 });

src/subject.vala

@@ -2,6 +2,7 @@ public class Subject : Object{
     public string name { get; set; }
     public ListStore grades_model { get; construct; }
     public HashTable<string, Category> categories_by_name { get; construct; }
+    public bool deleted { get; set; default = false; }
 
     public Subject (string name) {
         Object (name: name);

src/window.vala

@@ -58,6 +58,12 @@ public class Window : Adw.ApplicationWindow {
         subject_manager.read_data ();
 
         foreach (var subject in subject_manager.subjects.get_values ()) {
+            subject.notify["deleted"].connect (() => {
+                if (subject.deleted) {
+                    //TODO: Remove without crash
+                }
+                warning ("removed");
+            });
             stack.add_titled (new SubjectPage (subject), subject.name, subject.name);
         }