Nil panic calling `Session.ID()`

[imiric]

This seems to be a new flaky nil panic :disappointed: Spotted 2 times in #508 (job #1237 and #1240):

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x112daaa]

goroutine 1155 [running]:
github.com/grafana/xk6-browser/common.(*Session).ID(0x0)
	/home/runner/work/xk6-browser/xk6-browser/common/session.go:77 +0x2a
github.com/grafana/xk6-browser/common.(*Page).sessionID(...)
	/home/runner/work/xk6-browser/xk6-browser/common/page.go:922
github.com/grafana/xk6-browser/common.NewPage({0x1cace60?, 0xc0006548d0}, {0x1cb1d10?, 0x0}, 0xc000706b40, {0xc0000486c0, 0x20}, 0x0, 0x1, 0xc000705e30)
	/home/runner/work/xk6-browser/xk6-browser/common/page.go:129 +0x7f1
github.com/grafana/xk6-browser/common.(*Browser).onAttachedToTarget(0xc000447e00, 0xc00065c0a0)
	/home/runner/work/xk6-browser/xk6-browser/common/browser.go:287 +0xacf
github.com/grafana/xk6-browser/common.(*Browser).initEvents.func1()
	/home/runner/work/xk6-browser/xk6-browser/common/browser.go:194 +0x425
created by github.com/grafana/xk6-browser/common.(*Browser).initEvents
	/home/runner/work/xk6-browser/xk6-browser/common/browser.go:179 +0x35e
FAIL	github.com/grafana/xk6-browser/tests	5.593s
?   	github.com/grafana/xk6-browser/tests/ws	[no test files]

It happened in different tests, TestLocator/DispatchEvent and TestElementHandleBoundingBoxInvisibleElement.

We do a nil check before calling session.ID(): https://github.com/grafana/xk6-browser/blob/67499f7b2608ada93d467ff8fc1c4890c09d559e/common/page.go#L920-L923

But I suppose it's possible for that to race and session to be nil after it? This is only called for logging, though session shouldn't be nil at that point... :thinking: