Null Pointer Deference in HeadlessExample

[Jesse Hertz]

Hi All:

It appears (at least for me), that HeadlessExample is broken. When I try to run it, I get a null pointer dereference, see the following backtrace in lldb:

```

(lldb) run google.com
Process 62986 launched: '/Users/jhertz/a/chromium/src/out/a/headless_example' (arm64)
2022-08-25 21:47:08.701640-0400 headless_example[62986:25455662] [] [0x133030620] CVCGDisplayLink::setCurrentDisplay: 1
2022-08-25 21:47:08.701897-0400 headless_example[62986:25455662] [] [0x133030600] CVDisplayLinkCreateWithCGDisplays count: 1 [displayID[0]: 0x1] [CVCGDisplayLink: 0x133030620]
2022-08-25 21:47:08.701907-0400 headless_example[62986:25455662] [] [0x133030620] CVCGDisplayLink::finalize
2022-08-25 21:47:08.701910-0400 headless_example[62986:25455662] [] [0x133030620] CVDisplayLink::finalize
headless_example was compiled with optimization - stepping may behave oddly; variables may not be available.
Process 62986 stopped
* thread #1, name = 'CrBrowserMain', queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x0)
    frame #0: 0x0000000100004b44 headless_example`OnHeadlessBrowserStarted(headless::HeadlessBrowser*) [inlined] HeadlessExample::HeadlessExample(this=0x000060000172a200, browser=0x0000000129e05260, web_contents=0x0000000000000000) at headless_example.cc:72:18 [opt]
   69          : browser_(browser),
   70            web_contents_(web_contents),
   71            devtools_client_(headless::HeadlessDevToolsClient::Create()) {
-> 72        web_contents_->AddObserver(this);
   73      }
   74      
   75      HeadlessExample::~HeadlessExample() {
Target 0: (headless_example) stopped.

```

I am on the newest version of chromium (fbc0ddb4f4289d7a27676496c68780e1aa5d6607) at this time, and while I am writing a new headless module, I have not made any modifications to headless_example other than inserting a single line:

`  builder.SetDisableSandbox(true);`

to stop it from complaining about not having a valid Seatbelt profile.

OS: MacOS (ARM) 12.3

Thanks!

-jh

[Zoe Clifford]

Hello,

I believe you may be running into this code path. If the URL is invalid, then the web contents will be null, and you'll get a null pointer deference.

Does it work if you instead write run https://www.google.com/?

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[Jesse Hertz]

Ah! What a dumb mistake. Thank you :)

I am having an actual issue with headless chrome in an app I'm working on, but I suppose I'll start another thread. 

Thanks again!

[Jerry Lee Daniel]

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