Requests are not processed when sleeping with authenticated proxies

```
from seleniumbase import SB

with SB(uc=True, proxy=open("proxy.txt").read()) as sb: # remove the proxy for it to load normally
    sb.activate_cdp_mode('about:blank')
    sb.open('https://yog9.github.io/SnapShot/#/SnapScout/mountain')
    sb.sleep(10) # No images are loaded
```
