fixed wxDataInputStream::ReadString for empty strings

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@6442 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/datstrm.cpp

@@ -90,6 +90,8 @@ wxString wxDataInputStream::ReadString()
 
   len = Read32();
 
+  if (len > 0)
+  {
 #if wxUSE_UNICODE
     char *tmp = new char[len + 1];
     m_input->Read(tmp, len);
@@ -101,9 +103,11 @@ wxString wxDataInputStream::ReadString()
     m_input->Read(s.GetWriteBuf(len), len);
     s.UngetWriteBuf();
 #endif
-
     return s;
   }
+  else 
+    return wxEmptyString;
+}
 
 wxDataInputStream& wxDataInputStream::operator>>(wxString& s)
 {
@@ -203,7 +207,8 @@ void wxDataOutputStream::Write8(wxUint8 i)
 void wxDataOutputStream::WriteString(const wxString& string)
 {
   const wxWX2MBbuf buf = string.mb_str();
-  Write32(string.Length());
+  Write32(string.Len());
+  if (string.Len() > 0)
       m_output->Write(buf, string.Len());
 }