string_utils: don't add null byte to wide strings

Fixes call recording in windows. The filename was cut short by the null
byte inserted before the filename and extension.

Change-Id: I502d5f4c0360b19ea58ebb1fffbc61ec41567dfa

src/string_utils.cpp

@@ -39,7 +39,7 @@ namespace jami {
 std::wstring
 to_wstring(const std::string& s)
 {
-    int slength = (int)s.length() + 1;
+    int slength = (int)s.length();
     int len = MultiByteToWideChar(CP_UTF8, 0, s.c_str(), slength, nullptr, 0);
     if (not len)
         throw std::runtime_error("Can't convert string to wchar");