Fix browserContext.options nil panic

[Sacrond]

This is to fix the following issue.

#360

[canstand]

add just these 3 lines to browser_context.go should work, please test

func (b *browserContextImpl) setOptions(options *BrowserNewContextOptions, tracesDir *string) {
	if options == nil {   // line 543
		options = &BrowserNewContextOptions{}
	}
	b.options = options

[Sacrond]

Adding the 3 lines mentioned to browser_context.go does seem to fix the issue. Updated the commit to just append the 3 lines instead.

[canstand]

@mxschmitt