Janitor/MemBufInputSource crash

When parsing a document that contains an external subset, the parser crashes in
the destructor in MemBufInputSource. Looking in the source code, it seems to me
that a Janitor is set twice on the input source; once in
ReaderMgr::createReader method and once in the DTDScanner::scanDocTypeDecl
method. When I then commented out the Janitor-statement on line 1744 in
DTDScanner::scanDocTypeDecl, it worked fine.