Issue #3509590: Allow trailing whitespace in the query

Closes #3509590

src/Utility/AutocompleteHelper.php

@@ -27,10 +27,9 @@ class AutocompleteHelper implements AutocompleteHelperInterface {
    */
   public function splitKeys($keys) {
     $keys = ltrim($keys);
-    // If there is whitespace or a quote on the right, all words have been
-    // completed.
-    if (rtrim($keys, " \"") != $keys) {
-      return [rtrim($keys, ' '), ''];
+    // If there is a quote on the right, all words have been completed.
+    if (rtrim($keys, "\"") != $keys) {
+      return [$keys, ''];
     }
     if (preg_match('/^(.*?)\s*"?([\S]*)$/', $keys, $m)) {
       return [$m[1], $m[2]];