feat: improve errors when entity is unavailable

assets/tests/insert_children/invalid_entity_errors.lua

@@ -1,4 +1,4 @@
-local fake_entity = Entity.from_raw(9999)
+local fake_entity = Entity.from_raw(0)
 
 assert_throws(function()
     world.insert_children(fake_entity, 1, {fake_entity})

assets/tests/insert_children/invalid_entity_errors.rhai

@@ -1,4 +1,4 @@
-let fake_entity = Entity.from_raw.call(9999);
+let fake_entity = Entity.from_raw.call(0);
 
 assert_throws(||{
     world.insert_children.call(fake_entity, 0, [fake_entity]);

crates/bevy_mod_scripting_core/src/bindings/world.rs

@@ -536,7 +536,7 @@ impl<'w> WorldAccessGuard<'w> {
     /// checks if a given entity exists and is valid
     pub fn is_valid_entity(&self, entity: Entity) -> Result<bool, InteropError> {
         let cell = self.as_unsafe_world_cell()?;
-        Ok(cell.get_entity(entity).is_some())
+        Ok(cell.get_entity(entity).is_some() && entity.index() != 0)
     }
 
     /// Tries to call a fitting overload of the function with the given name and in the type id's namespace based on the arguments provided.

crates/lad_backends/mdbook_lad_preprocessor/src/sections.rs

@@ -622,6 +622,7 @@ impl IntoMarkdown for SectionItem<'_> {
                         </div>
                     "#.trim(),
                     );
+                    builder.append("\n\n");
                 }
 
                 // we don't escape this, this is already markdown