Fix potencial get_stackdata call before on_activate call. Update doc.

doc/lua_api.md

@@ -5948,8 +5948,11 @@ Environment access
 * `minetest.add_entity(pos, name, [staticdata])`: Spawn Lua-defined entity at
   position.
     * Returns `ObjectRef`, or `nil` if failed
+    * Entities with `static_save = true` can be added also 
+      to unloaded/nongenerated blocks.
 * `minetest.add_item(pos, item)`: Spawn item
     * Returns `ObjectRef`, or `nil` if failed
+    * Items can be added also to unloaded/nongenerated blocks.
 * `minetest.get_player_by_name(name)`: Get an `ObjectRef` to a player
 * `minetest.get_objects_inside_radius(pos, radius)`: returns a list of
   ObjectRefs.

src/serverenvironment.cpp

@@ -1901,6 +1901,11 @@ u16 ServerEnvironment::addActiveObjectRaw(std::unique_ptr<ServerActiveObject> ob
 		return 0;
 	}
 
+	// Register reference in scripting api (must be done before post-init)
+	m_script->addObjectReference(object);
+	// Post-initialize object
+	object->addedToEnvironment(dtime_s);
+
 	// Add static data to block
 	if (object->isStaticAllowed()) {
 		// Add static object to active static list of the block
@@ -1922,16 +1927,14 @@ u16 ServerEnvironment::addActiveObjectRaw(std::unique_ptr<ServerActiveObject> ob
 			errorstream << "ServerEnvironment::addActiveObjectRaw(): "
 				<< "could not emerge block " << p << " for storing id="
 				<< object->getId() << " statically" << std::endl;
+			// clean in case of error
+			object->removingFromEnvironment();
+			m_script->removeObjectReference(object);
 			m_ao_manager.removeObject(object->getId());
 			return 0;
 		}
 	}
 
-	// Register reference in scripting api (must be done before post-init)
-	m_script->addObjectReference(object);
-	// Post-initialize object
-	object->addedToEnvironment(dtime_s);
-
 	return object->getId();
 }