Fixed bug: If a field of a filter had no value it would throw a core exception because no pattern with an empty value could be created. Now the value gets trimmed and in case of emptyness ignored.
Workaround, if the prefilter json contains an empty value it gets translated to null by indexsearch.buildQueryFromSearchCondition with which nothing would be found. The null value now gets temporarily replaced. Hast to be removed when the api has been fixed!
Specific line to remove:
indexPattern = indexPattern.replace(null, "");//todo remove if api has been fixed