If backend is not accessible, `Diagnostic data` can't be opened

[Alex-302]

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• [X] I am running the latest version
• [X] I checked the documentation and found no answer
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AdGuard VPN version

2.3.0 n25

Operating mode

VPN

Environment

- OS: Windows 10 x64
- Other network-level software: no

Issue Details

Steps to reproduce:

1. Try to open Diagnostic data when backend is is not accessible

Expected Behavior

Works

Actual Behavior

Nothing happens after clicks.

Screenshots

No response

Additional Information

No response