fix(browser): fixed state lose in extendState method

[Zheleznyak-F]

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• [x] The commit message follows Conventional Commits
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• [x] Bugfix
• [ ] Feature
• [ ] Refactoring (no functional changes, no api changes)
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It is a fix this issue https://github.com/Tinkoff/micro-sentry/issues/37

[tinkoff-bot]

:tada: This pull request is included in version browser@6.0.2 :tada:

The release is available on GitHub release

[tinkoff-bot]

:tada: This pull request is included in version core@6.0.3 :tada:

The release is available on GitHub release

[tinkoff-bot]

:tada: This pull request is included in version angular@6.1.5 :tada:

The release is available on GitHub release