Steps to reproduce when it comes to Image Variations: doesn't occur in v2.5

1. just follow the steps from the linked issue.

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When it comes to Content Types:

1. Create Content Type with name "1234".
2. Try to generate schema.

Result:
The schema will not be generated properly.

Expected result:
The schema will skip a generation of wrongly named Content Types.

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When it comes to blocks' views' names:

1. Name the view of the custom block like 44.
2. Generate schema.

Result:
Symfony container is broken (nothing can be accessed).

Expected result:
There shouldn't be any exception in the Back Office.