Fix exception when searching (#7659)

* repair issue7343

* change CHANGELOG.md

* change style

* change cleanup

* Update CHANGELOG.md

Co-authored-by: Christoph <siedlerkiller@gmail.com>

CHANGELOG.md

@@ -540,6 +540,7 @@ Note that this project **does not** adhere to [Semantic Versioning](http://semve
 - We fixed an issue where the "Search for unlinked local files" would throw an exception when parsing the content of a PDF-file with missing "series" information [#5128](https://github.com/JabRef/jabref/issues/5128)
 - We fixed an issue where the XMP Importer would incorrectly return an empty default entry when importing pdfs [#6577](https://github.com/JabRef/jabref/issues/6577)
 - We fixed an issue where opening the menu 'Library properties' marked the library as modified [#6451](https://github.com/JabRef/jabref/issues/6451)
+- We fixed an issue when importing resulted in an exception [#7343](https://github.com/JabRef/jabref/issues/7343)
 
 ### Removed
 

src/main/java/org/jabref/logic/importer/ImportCleanup.java

@@ -33,6 +33,6 @@ public BibEntry doPostCleanup(BibEntry entry) {
      * Performs a format conversion of the given entry collection into the targeted format.
      */
     public void doPostCleanup(Collection<BibEntry> entries) {
-        entries.parallelStream().forEach(entry -> doPostCleanup(entry));
+        entries.forEach(this::doPostCleanup);
     }
 }