title: ORA-64451: Conversion of special character to escaped character failed
body: <p>I am concatenating some texts and I get this weird error that I can't find anything about</p>
  
  <pre><code>UPDATE Table1 a
  SET a.AllTexts = a.Text
    || a.Title
    ||
    (SELECT XMLAGG(XMLELEMENT(E,"Text",',').EXTRACT('//text()')).GetClobVal()
    FROM Table2 b
    WHERE b.El_Id = a.Id
    )
  </code></pre>
  
  <p>AllTexts is <code>CLOB</code>, all other columns are <code>VARCHAR2</code></p>
  
  <p>I get </p>
  
  <pre><code>Error report -
  SQL Error: ORA-64451: Conversion of special character to escaped character failed.
  64451. 00000 -  "Conversion of special character to escaped character failed."
  *Document: NO
  *Cause:    An attempt to convert a special character to an escaped character failed.
  *Action:   Remove the special character that cannot be escaped.
  </code></pre>
  
  <p><strong>Edit:</strong> the error is caused by some weird symbols. Problem is there is no way to know ahead which symbols will block execution</p>