tinyxml2 can't load my xml file

I'm using tinyxml2 in my after effects plugin to parse xml files. But I can't seem to get the XMLDocument object to load my xml file. The "loadFile" function can read the whole content of my file. but when I call the "toText" method, it returns null. Here's a snippet of my code.

tinyxml2::XMLDocument  envXml;
envXml.LoadFile("D:/~env.xml");
XMLText*text = envXml.ToText();//return null  
XMLNode*srcChild = envXml.LastChild();
XMLElement*srcElement = srcChild->ToElement();// crash

here's my xml file content:

<xml>
     <rs_tpl>some text 
          <t>test</t>
     </rs_tpl>
     <logo_path>some text</logo_path>
     <src>some text</src>
     <dst>some text</dst>
     <out_path>some text</out_path>
     <out_comp>some text</out_comp>
</xml>

What I'm doing wrong?