Issue #3362991 by nevergone: Unicode-compatible regexp with better matching

src/Plugin/Filter/TrimHtml.php

@@ -23,7 +23,7 @@ class TrimHtml extends FilterBase {
   public function process($text, $langcode) {
     // Remove all <br/> and empty (i.e. containing only whitespace or &nbsp;)
     // <p> tags from the end of $text.
-    $pattern = '/((\s*<\s*p\s*>(&nbsp;|\s)*<\s*\/p\s*>\s*)|(\s*<\s*br\s*\/\s*>\s*))*$/';
+    $pattern = '/((\s*)|((?:<\s*p\s*>\s*(&nbsp;|\s)*<\s*\/p\s*>\s*)*)|(\s*<\s*br\s*\/\s*>\s*))*$/ui';
     $text = preg_replace($pattern, '', $text);
     return new FilterProcessResult($text);
   }