Fix null handling if no project is open in web api

PlayWallPlugins/PlayWallPluginWebAPI/src/main/scala/de/tobias/playpad/plugin/api/websocket/methods/ProjectCurrentMethod.scala

@@ -11,6 +11,10 @@ class ProjectCurrentMethod extends MethodExecutable {
 	override def execute(session: Session, message: Message): JsonObject = {
 		val currentProject = PlayPadPlugin.getInstance().getCurrentProject
 
+		if (currentProject == null) {
+			new JsonObject
+		} else {
 			ProjectSerializer.serializeProject(currentProject)
 		}
 	}
+}