io.c (io_encoding_set): typo fixed

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@14976 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

io.c

@@ -5627,7 +5627,7 @@ io_encoding_set(rb_io_t *fptr, int argc, VALUE v1, VALUE v2)
 	fptr->enc = rb_to_encoding(v2);
     }
     else if (argc == 1) {
-	if if (NIL_P(v1)) {
+	if (NIL_P(v1)) {
 	    fptr->enc = 0;
 	}
 	else {