correct empty return call (closes #588)

Author: eddelbuettel

ChangeLog

@@ -1,3 +1,7 @@
+2016-11-13  Dirk Eddelbuettel  <[email protected]>
+
+        * R/Attributes.R (mergeIntoBuildEnv): Correct 'empty' return 
+
 2016-11-10  Dirk Eddelbuettel  <[email protected]>
 
         * inst/include/Rcpp/date_datetime/newDateVector.h: Added constructor

R/Attributes.R

@@ -618,15 +618,15 @@ sourceCppFunction <- function(func, isVoid, dll, symbol) {
 
         # protect against null or empty string
         if (is.null(value) || !nzchar(value))
-            return;
+            return(invisible(NULL))
 
         # if it doesn't exist already just set it
         if (is.null(buildEnv[[name]])) {
             buildEnv[[name]] <<- value
         }
         # if it's not identical then append
         else if (!identical(buildEnv[[name]], value)) {
-            buildEnv[[name]] <<- paste(buildEnv[[name]], value);
+            buildEnv[[name]] <<- paste(buildEnv[[name]], value)
         }
         else {
             # it already exists and it's the same value, this