BUGFIX: Trim leading and tailing whitespaces

Whitespaces like a tab can lead to a 404 error if a URL has been pasted to a LinkEditor or LinkInput.

As datasources, assets, URLs and slugs should not start with a whitespace, we can remove them.

Fixes: #3859

packages/neos-ui-editors/src/Library/LinkInput.js

@@ -149,6 +149,10 @@ export default class LinkInput extends PureComponent {
     }
 
     handleSearchTermChange = searchTerm => {
+        // trim leading and trailing whitespace as it can cause issues
+        // with the further processing
+        searchTerm.trim()
+
         this.setState({searchTerm});
 
         if (isUriOrInternalLink(searchTerm)) {