LibGUI: Fix for disable state of SpinBox

Author: https://github.com/asliturk
Commit: https://github.com/SerenityOS/serenity/commit/f0f98de5d81
Pull-request: https://github.com/SerenityOS/serenity/pull/2146

Libraries/LibGUI/SpinBox.cpp

@@ -87,6 +87,15 @@ void SpinBox::set_range(int min, int max)
     update();
 }
 
+void SpinBox::set_enabled(bool value)
+{
+    Widget::set_enabled(value);
+
+    m_editor->set_enabled(value);
+    m_increment_button->set_enabled(value);
+    m_decrement_button->set_enabled(value);
+}
+
 void SpinBox::keydown_event(KeyEvent& event)
 {
     if (event.key() == KeyCode::Key_Up) {

Libraries/LibGUI/SpinBox.h

@@ -44,6 +44,8 @@ public:
     void set_max(int max) { set_range(min(), max); }
     void set_range(int min, int max);
 
+    void set_enabled(bool);
+
     Function<void(int value)> on_change;
 
 protected: