About word to html about vMerge's xml parsing problem when line merging

[raybon-lee]

After testing, it was found that the line merging vMerge in the latest version of word2007 is no longer w:val=“continue” but <w:vMerge />, so when you need to parse Xml, you need to give the default value condition to facilitate the word .docx format Converting html will not have the problem of not merging lines, colspan can't work properly

start :
<w:vMerge w:val="restart"/>

next row cell default is continue
<w:vMerge/>

[raybon-lee]

PR: #2250