BUG: Organizations field gets infilled with null

## 🐛 Bug Report Organizations field gets infilled with null

### What went wrong? 🤔
In production when someone was creating an event they infilled 'organization' filled somehow with null.
This broke view with a list of created events and possibly other things as well

### Expected Behavior
When creating an event 'organizations' field shouldn't be able to be null

### Actual Behavior
When creating an event 'organizations' field got filled with null

### Steps to Reproduce Issue

### Solution

### Environment

#### Operating System

#### Browser

### Screenshots

未提供文件、测试或复现步骤。首先复现使用空组织值创建事件的过程，然后跟踪事件创建流程和已创建事件视图。当组织无法以 null 的形式存储且事件列表能够正确渲染时，即视为完成。

由索引模型根据 Issue 内容生成。