QueryParser escaping/parsin issue with strings starting/ending with ||

There is a problem with query parser when search string starts/ends with ||. When string contains || in the middle like 'something || something' everything runs without a problem.

Part of code:
searchText = QueryParser.escape(searchText);
QueryParser parser = null;
parser = new QueryParser(fieldName, new CustomAnalyser());
parser.parse(searchText);

CustomAnalyser class extends Analyser. Here is the only redefined method:

@Override
public TokenStream tokenStream(String fieldName, Reader reader)

{ return new PorterStemFilter( (new StopAnalyzer()).tokenStream(fieldName, reader)); }

I have tested this on Lucene 2.1 and latest source I have checked-out from SVN (Revision 538867) and in both cases parsing exception was thrown.

Part of Stack Trace (Lucene - SVN checkout - Revision 538867):
Cannot parse 'someting ||': Encountered "<EOF>" at line 1, column 11.
Was expecting one of:
<NOT> ...
"+" ...
"-" ...
"(" ...
"*" ...
<QUOTED> ...
<TERM> ...
<PREFIXTERM> ...
<WILDTERM> ...
"[" ...
"{" ...
<NUMBER> ...

org.apache.lucene.queryParser.ParseException: Cannot parse 'someting ||': Encountered "<EOF>" at line 1, column 11.
Was expecting one of:
<NOT> ...
"+" ...
"-" ...
"(" ...
"*" ...
<QUOTED> ...
<TERM> ...
<PREFIXTERM> ...
<WILDTERM> ...
"[" ...
"{" ...
<NUMBER> ...

at org.apache.lucene.queryParser.QueryParser.parse(QueryParser.java:150)

Part of Stack Trace (Lucene 2.1):
Cannot parse 'something ||': Encountered "<EOF>" at line 1, column 12.
Was expecting one of:
<NOT> ...
"+" ...
"-" ...
"(" ...
"*" ...
<QUOTED> ...
<TERM> ...
<PREFIXTERM> ...
<WILDTERM> ...
"[" ...
"{" ...
<NUMBER> ...

org.apache.lucene.queryParser.ParseException: Cannot parse 'something ||': Encountered "<EOF>" at line 1, column 12.
Was expecting one of:
<NOT> ...
"+" ...
"-" ...
"(" ...
"*" ...
<QUOTED> ...
<TERM> ...
<PREFIXTERM> ...
<WILDTERM> ...
"[" ...
"{" ...
<NUMBER> ...

at org.apache.lucene.queryParser.QueryParser.parse(QueryParser.java:149)