hyphenator valgrind error

==30983== Invalid read of size 1
==30983==    at 0x81151B6: fl_utf8back (fl_utf.c:259)
==30983==    by 0x80A2320: dw::fltk::FltkPlatform::prevGlyph(char const*, int) (fltkplatform.cc:599)
==30983==    by 0x809EDA3: dw::Hyphenator::hyphenateSingleWord(dw::core::Platform*, char*, int, lout::misc::SimpleVector<int>*) (hyphenator.cc:327)
==30983==    by 0x809E9F2: dw::Hyphenator::hyphenateWord(dw::core::Platform*, char const*, int*) (hyphenator.cc:256)
==30983==    by 0x809C087: dw::Textblock::hyphenateWord(int) (textblock_linebreaking.cc:762)
==30983==    by 0x809BB6E: dw::Textblock::wordWrap(int, bool) (textblock_linebreaking.cc:609)
==30983==    by 0x809B6A9: dw::Textblock::processWord(int) (textblock_linebreaking.cc:441)
==30983==    by 0x8098753: dw::Textblock::addText0(char const*, unsigned int, short, dw::core::style::Style*, dw::core::Requisition*) (textblock.cc:1694)
==30983==    by 0x8097B02: dw::Textblock::addText(char const*, unsigned int, dw::core::style::Style*) (textblock.cc:1478)
==30983==    by 0x8073F5C: Html_process_word(DilloHtml*, char const*, int) (html.cc:1216)
==30983==    by 0x807A348: Html_write_raw(DilloHtml*, char*, int, int) (html.cc:3923)
==30983==    by 0x80727A9: DilloHtml::write(char*, int, int) (html.cc:531)
==30983==  Address 0x661e6bf is 1 bytes before a block of size 16 alloc'd
==30983==    at 0x402AC41: malloc (vg_replace_malloc.c:270)
==30983==    by 0x80A223F: dw::fltk::FltkPlatform::textToLower(char const*, int) (fltkplatform.cc:584)
==30983==    by 0x809E86A: dw::Hyphenator::hyphenateWord(dw::core::Platform*, char const*, int*) (hyphenator.cc:223)
==30983==    by 0x809C087: dw::Textblock::hyphenateWord(int) (textblock_linebreaking.cc:762)
==30983==    by 0x809BB6E: dw::Textblock::wordWrap(int, bool) (textblock_linebreaking.cc:609)
==30983==    by 0x809B6A9: dw::Textblock::processWord(int) (textblock_linebreaking.cc:441)
==30983==    by 0x8098753: dw::Textblock::addText0(char const*, unsigned int, short, dw::core::style::Style*, dw::core::Requisition*) (textblock.cc:1694)
==30983==    by 0x8097B02: dw::Textblock::addText(char const*, unsigned int, dw::core::style::Style*) (textblock.cc:1478)
==30983==    by 0x8073F5C: Html_process_word(DilloHtml*, char const*, int) (html.cc:1216)
==30983==    by 0x807A348: Html_write_raw(DilloHtml*, char*, int, int) (html.cc:3923)
==30983==    by 0x80727A9: DilloHtml::write(char*, int, int) (html.cc:531)
==30983==    by 0x8079D85: Html_callback(int, _CacheClient*) (html.cc:3799)