After launching ComfyUI for a while, the "Load Image" node cannot identify WebP.

### Expected Behavior

"Load Image" can support various common formats, such as jpeg, png, webp

### Actual Behavior

When loading a webp format image, an error message appears, indicating that the image cannot be recognized. In fact, the image is normal.

```
[2024-07-10 11:34] got prompt
[2024-07-10 11:34] [rgthree] Using rgthree's optimized recursive execution.
[2024-07-10 11:34] !!! Exception during processing!!! local variable 'x' referenced before assignment
[2024-07-10 11:34] Traceback (most recent call last):
File "/root/work_py/ComfyUI/node_helpers.py", line 16, in pillow
x = fn(arg)
File "/root/.conda/envs/comfyui/lib/python3.10/site-packages/PIL/Image.py", line 3298, in open
elif hasattr(obj, "tostring"):
PIL.UnidentifiedImageError: cannot identify image file '/root/work_py/ComfyUI/input/abc.webp'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/root/work_py/ComfyUI/node_helpers.py", line 20, in pillow
x = fn(arg)
File "/root/.conda/envs/comfyui/lib/python3.10/site-packages/PIL/Image.py", line 3298, in open
elif hasattr(obj, "tostring"):
PIL.UnidentifiedImageError: cannot identify image file '/root/work_py/ComfyUI/input/abc.webp'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/root/work_py/ComfyUI/execution.py", line 151, in recursive_execute
output_data, output_ui = get_output_data(obj, input_data_all)
File "/root/work_py/ComfyUI/execution.py", line 81, in get_output_data
return_values = map_node_over_list(obj, input_data_all, obj.FUNCTION, allow_interrupt=True)
File "/root/work_py/ComfyUI/execution.py", line 74, in map_node_over_list
results.append(getattr(obj, func)(**slice_dict(input_data_all, i)))
File "/root/work_py/ComfyUI/nodes.py", line 1462, in load_image
img = node_helpers.pillow(Image.open, image_path)
File "/root/work_py/ComfyUI/node_helpers.py", line 24, in pillow
return x
UnboundLocalError: local variable 'x' referenced before assignment

[2024-07-10 11:34] Prompt executed in 0.04 seconds
```

### Steps to Reproduce

webp img:
workflow: [workflow.json](https://github.com/user-attachments/files/16154905/workflow.json)

example

- Load workflow
- ”Load image“ Upload a Webp image
- Click "Queue Prompt"

### Debug Logs

```powershell
System Info:
Operating System: CentOS Linux 7 (Core)
CPE OS Name: cpe:/o:centos:centos:7
Kernel: Linux 3.10.0-1160.118.1.el7.x86_64
Architecture: x86-64
```

```
Python Env Info:
Python Env: Python 3.10.6
pillow==10.4.0
```

```
Python 3.10.6 (main, Oct 24 2022, 16:07:47) [GCC 11.2.0]
Type 'copyright', 'credits' or 'license' for more information
IPython 8.25.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]: from PIL import features
...: print (features.check_module('webp'))
True

```
```

### Other

When the service is just started, it can parse the Webp format. After running for a while, it cannot parse Webp. Other image formats are normal. After restarting ComfyUI, it returns to normal. The image with the error can be loaded normally by executing PIL.Image.Open("abc.webp") in the terminal.