top: fix "warning: unused variable new_mask"

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/procps/top.c b/procps/top.c
index 075c96c..1b49a5e 100644
--- a/procps/top.c
+++ b/procps/top.c
@@ -1157,7 +1157,7 @@
 #endif
 
 	while (scan_mask != EXIT_MASK) {
-		unsigned new_mask;
+		IF_FEATURE_TOP_INTERACTIVE(unsigned new_mask;)
 		procps_status_t *p = NULL;
 
 		if (OPT_BATCH_MODE) {