[Bug]: A frame with an empty url will dead-loop

[Konano]

Playwright version

1.15.2-1633455481000

Operating system

Linux

What browsers are you seeing the problem on?

Chromium

Other information

No response

What happened? / Describe the bug

A frame with an empty url will dead-loop.

Code snippet to reproduce your bug

from playwright.sync_api import sync_playwright

def run(playwright):
    chromium = playwright.chromium # or "firefox" or "webkit".
    browser = chromium.launch()
    page = browser.new_page()
    page.goto("file:///var/www/html/index.html")
    for x in page.frames:
        print(x.url)
        print(x.content())
    browser.close()

with sync_playwright() as playwright:
    run(playwright)

/var/www/html/index.html:

<iframe src="javascript:false" title="" frameborder="0" tabindex="-1" style="position: absolute; width: 0px; height: 0px; border: 0px;"></iframe>

Relevant log output

Traceback (most recent call last):
  File "test.py", line 15, in <module>
  File "test.py", line 10, in run
    print(x.content())
  File "/home/nano/.local/lib/python3.8/site-packages/playwright/sync_api/_generated.py", line 3797, in content
    self._sync("frame.content", self._impl_obj.content())
  File "/home/nano/.local/lib/python3.8/site-packages/playwright/_impl/_sync_base.py", line 109, in _sync
    self._dispatcher_fiber.switch()
  File "/home/nano/.local/lib/python3.8/site-packages/playwright/sync_api/_context_manager.py", line 48, in greenlet_main
    loop.run_until_complete(self._connection.run_as_sync())
  File "/usr/lib/python3.8/asyncio/base_events.py", line 603, in run_until_complete
    self.run_forever()
  File "/usr/lib/python3.8/asyncio/base_events.py", line 570, in run_forever
    self._run_once()
  File "/usr/lib/python3.8/asyncio/base_events.py", line 1823, in _run_once
    event_list = self._selector.select(timeout)
  File "/usr/lib/python3.8/selectors.py", line 468, in select
    fd_event_list = self._selector.poll(timeout, max_ev)
KeyboardInterrupt

[dgozman]

This is probably the same as #8943.