refinement thanks to Kevin

Author: eddelbuettel

inst/include/Rcpp/macros/macros.h

@@ -100,8 +100,7 @@
   }                                                                            \
   UNPROTECT(nprot);                                                            \
   return R_NilValue;                                                           \
-  if (stop_sym == R_NilValue) /* never reached but */                          \
-    return R_NilValue;        /* suppresses warning*/
+  (void) stop_sym;   /* never reached but suppresses warning */
 #endif
 
 #define Rcpp_error(MESSAGE) throw Rcpp::exception(MESSAGE, __FILE__, __LINE__)