avm2: Movie clips not explicitly granted a `symbol_class` should be constructed using the `MovieClip` class directly

core/src/avm2/globals.rs

@@ -54,6 +54,7 @@ pub struct SystemPrototypes<'gc> {
     pub uint: Object<'gc>,
     pub namespace: Object<'gc>,
     pub array: Object<'gc>,
+    pub movieclip: Object<'gc>,
     pub framelabel: Object<'gc>,
     pub scene: Object<'gc>,
 }
@@ -83,6 +84,7 @@ impl<'gc> SystemPrototypes<'gc> {
             uint: empty,
             namespace: empty,
             array: empty,
+            movieclip: empty,
             framelabel: empty,
             scene: empty,
         }
@@ -384,7 +386,13 @@ pub fn load_player_globals<'gc>(activation: &mut Activation<'_, 'gc, '_>) -> Res
         flash::display::sprite::create_class(activation.context.gc_context),
         implicit_deriver,
     )?;
-    class(
+    activation
+        .context
+        .avm2
+        .system_prototypes
+        .as_mut()
+        .unwrap()
+        .movieclip = class(
         activation,
         gs,
         flash::display::movieclip::create_class(activation.context.gc_context),

core/src/display_object/movie_clip.rs

@@ -1497,8 +1497,12 @@ impl<'gc> MovieClip<'gc> {
         context: &mut UpdateContext<'_, 'gc, '_>,
         display_object: DisplayObject<'gc>,
     ) {
-        let constructor = self.0.read().avm_constructor;
-        if let Some(AvmObject::Avm2(mut constr)) = constructor {
+        let constructor = self
+            .0
+            .read()
+            .avm_constructor
+            .unwrap_or_else(|| context.avm2.prototypes().movieclip.into());
+        if let AvmObject::Avm2(mut constr) = constructor {
             let mut constr_thing = || {
                 let mut activation = Avm2Activation::from_nothing(context.reborrow());
                 let proto = constr
@@ -1527,7 +1531,7 @@ impl<'gc> MovieClip<'gc> {
                 log::error!("Got {} when constructing AVM2 side of display object", e);
             }
         } else {
-            log::error!("Attempted to construct AVM2 movieclip without constructor!");
+            log::error!("Attempted to construct AVM2 movieclip with AVM1 constructor!");
         }
     }