Clear incorrect values if needed on question validation in select base

[andrewtelnov]

No description provided.

[tylers]

I believe this change broke the ability to select options that were retrieved from external sources when applying the select2 processResults() method.

If you use select2 initialization with the tagbox element, then fetch new options based on the query/term entered. Once you select an option, you can verify the question will have it's value updated with SurveyJS's onValueChanged() method. But it will immediately remove that option from the value and onValueChanged() will fire again.

In this example:

• click on tagbox question and it opens the dropdown panel
• search for term '99'
• new options are fetched and added to the panel
• select a new option
• onValueChanged() is updated with value ['99']
• onValueChanged() is updated with value []

I'm not sure if this is the change that caused it but the functionality broke between 1.12.23 and 1.12.24 and this is the ticket that seems the most likely to have caused it. I don't have a sandbox to demonstrate and I couldn't find an example that retrieves options with select2 on the site to extend.

Issue 9603 created

@tsv2013