Use xlengthgets instead of SETLENGTH.

git-svn-id: https://svn.r-project.org/R/trunk@89073 00db46b3-68df-0310-9c12-caf00c1e9a41

Author: luke

src/library/grid/src/unit.c

@@ -1752,7 +1752,7 @@ SEXP matchUnit(SEXP units, SEXP unit) {
 			count++;
 		}
 	}
-	SETLENGTH(matches, count);
+	matches = xlengthgets(matches, count);
 	UNPROTECT(1);
 	return matches;
 }