Parameter must be an array or an object that implements Countable in SearchApiSolrBackend->setAutocompleteSuggesterQuery()

Problem/Motivation

Since the languages on a solr query could be NULL, the we get the following notice in the logs when this is the case:
Parameter must be an array or an object that implements Countable in SearchApiSolrBackend->setAutocompleteSuggesterQuery()

Proposed resolution

Add a check if languages is not empty.

Remaining tasks

User interface changes

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API changes

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Data model changes

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Release notes snippet