Don't remove error message when the field becomes valid

[denis-anisimov]

Fix for #3439

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This change is 

[caalador]

Reviewed 4 of 4 files at r1.
Review status: all files reviewed at latest revision, all discussions resolved.

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Comments from Reviewable

[vaadin-bot]

SonarQube analysis reported 53 issues

• 3 critical
• 19 major
• 31 minor

Top 10 extra issues

Note: The following issues were found on lines that were not modified in the pull request. Because these issues can't be reported as line comments, they are summarized here:

1. Binder.java#L1299: Move this constructor to comply with Java Code Conventions.
2. Binder.java#L2418: Either log or rethrow this exception.
3. Binder.java#L2479: Either log or rethrow this exception.
4. Binder.java#: This file has 1,017 lines, which is greater than 750 authorized. Split it into smaller files.
5. Binder.java#L116: Remove usage of generic wildcard type.
6. Binder.java#L116: Remove usage of generic wildcard type.
7. Binder.java#L190: Remove usage of generic wildcard type.
8. Binder.java#L190: Remove usage of generic wildcard type.
9. Binder.java#L761: Define and throw a dedicated exception instead of using a generic one.
10. Binder.java#L802: Prefix this call to "withValidator" with "super.".