message: core: fixed error message to avoid confusion
diff: @@ -716,7 +716,7 @@ public:
  else if(strncmp( bufPtr, xml_signature, strlen(xml_signature) ) == 0)
  fmt = FileStorage::FORMAT_XML;
  else if(strbufsize == bufOffset)
  - CV_Error(CV_BADARG_ERR, "Input file is empty");
  + CV_Error(CV_BADARG_ERR, "Input file is invalid");
  else
  CV_Error(CV_BADARG_ERR, "Unsupported file storage format");
  