viv-243: duplication of styles when scheme misconfigured

[gullerya]

Describe the bug
It might wrongly happen that scheme service is initialised more than once - in this case the scheme will install multiple styles which is bad and can be prevented.

To Reproduce
import vvd-scheme once with some specific query
import vvd-scheme second time with other query
observe the style elements and see that there are 2 styles installed

Expected behavior
in a case of duplicate init only 1 style should be installed
in a case of duplicate init error should be logged to the console

Screenshots
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Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
Add any other context about the problem here.