On vaadin 14.6 the style are not properly loaded

[ado2000]

Describe the bug
Migrating from vaadin 14.5 to 14.6, the left drawer is not properly styled.

To Reproduce
Steps to reproduce the behavior:
Use the layout add-on in vaadin 14.6, the left drawer is not properly styled.

Expected behavior
Load the style as in vaadin 14.5

Screenshots
Not correct in vaadin 14.6.8

Correct in vaadin 14.5.6

** Additional Information (please complete the following information):**

• OS: [osx]
• Browser [chrome, safari]
• Version 4.0.0

[jhult]

May not help for version 14, but version 22 is now supported with this PR: #445