Repository: stable-diffusion-webui
Issue: [Bug]:  The picture in process 90% is normal, but got a gray picture at last(txt2img). decode_first_stage function returned all 0
Labels: bug-report

### Is there an existing issue for this?

- [X] I have searched the existing issues and checked the recent builds/commits

### What happened?

I finetuned a stable diffusion v2.1 model, and run it. It looks normal in the progress 90% as follows(Nvidia T4 GPU 16G VRAM):
<img width="1363" alt="截屏2023-02-07 下午10 59 47" src="https://user-images.githubusercontent.com/92853025/217281508-f39ee887-19c6-430f-8a6a-df08ed1648ee.png">

But when after 97%, it returned a gray picture as follows:
<img width="1411" alt="截屏2023-02-07 下午10 59 59" src="https://user-images.githubusercontent.com/92853025/217281584-19d3f8a8-fad6-49ad-89cc-4a40ce45d3f2.png">

Could you tell me what is the problem?

### Steps to reproduce the problem

1. train a model of myself 
2. generate a picture using sd webui



### What should have happened?

get a normal picture

### Commit where the problem happens
It seems to have no problem from the text below, but the output is a gray picture:
the horrace sitting at a table in lingo room style Negative prompt: the tigoace Steps: 39, Sampler: Euler a, CFG scale: 7, Seed: 2562504435, Size: 768x577, Model hash: 9f58a10c2a, Model: 399

### What platforms do you use to access the UI ?

Linux

### What browsers do you use to access the UI ?

Google Chrome

### Command Line Arguments

```Shell
export COMMANDLINE_ARGS="--medvram  --precision full --no-half --disable-nan-check --opt-split-attention"
```


### List of extensions

No

### Console logs

```Shell
(stable-diffusion-webui) ubuntu@us-prod-liveroom-gpu-1:/data/stable-diffusion-webui$ ./webui.sh

################################################################
Install script for stable-diffusion + Web UI
Tested on Debian 11 (Bullseye)
################################################################

################################################################
Running on ubuntu user
################################################################

################################################################
Repo already cloned, using it as install directory
################################################################

################################################################
Create and activate python venv
################################################################

################################################################
Launching launch.py...
################################################################
Python 3.9.12 (main, Jun  1 2022, 11:38:51) 
[GCC 7.5.0]
Commit hash: ea9bd9fc7409109adcd61b897abc2c8881161256
Installing requirements for Web UI
############################
Launching Web UI with arguments: --medvram --precision full --no-half --disable-nan-check --opt-split-attention
No module 'xformers'. Proceeding without it.
Loading weights [9f58a10c2a] from /data/stable-diffusion-webui/models/Stable-diffusion/399.ckpt
Creating model from config: /data/stable-diffusion-webui/models/Stable-diffusion/399.yaml
LatentDiffusion: Running in v-prediction mode
DiffusionWrapper has 865.91 M params.
Applying cross attention optimization (Doggettx).
Textual inversion embeddings loaded(0): 
Model loaded in 36.6s (load weights from disk: 12.2s, create model: 22.8s, apply weights to model: 0.3s, load VAE: 0.9s, move model to device: 0.3s).
Running on local URL:  http://10.0.1.174:7860
Running on public URL: https://422b7689-37a1-4c60.gradio.live
This share link expires in 72 hours. For free permanent hosting and GPU upgrades (NEW!), check out Spaces: https://huggingface.co/spaces
100%|███████████████████████████████████████████████████████████████████████████████████████████████████████| 20/20 [00:12<00:00,  1.55it/s]
██████████████████████████████████████████████████████████████████████| 20/20 [00:08<00:00,  2.12it/s]
Total progress: 100%|███████████████████████████████████████████████████████████████████████████████████████| 20/20 [00:15<00:00,  1.28it/s]
```


### Additional information

_No response_