hush: plug a memory leak

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

shell/hush.c

@@ -4136,6 +4136,7 @@ static NOINLINE int run_pipe(struct pipe *pi)
 
 		/* if someone gives us an empty string: `cmd with empty output` */
 		if (!argv_expanded[0]) {
+			free(argv_expanded);
 			debug_leave();
 			return G.last_exitcode;
 		}

shell/hush_test/hush-z_slow/leak_empty_tick.right

@@ -0,0 +1,3 @@
+Warm up
+Measuring memory leak...
+Ok

shell/hush_test/hush-z_slow/leak_empty_tick.tests

@@ -0,0 +1,28 @@
+echo "Warm up"
+i=1
+while test $i != 9; do
+    `true`
+    : $((i++))
+done
+
+memleak
+
+echo "Measuring memory leak..."
+i=1
+while test $i != 199; do
+    `true`
+    : $((i++))
+done
+i=1
+while test $i != 199; do
+    `true`
+    : $((i++))
+done
+
+memleak
+kb=$?
+if test $kb -le 4; then
+    echo Ok #$kb
+else
+    echo "Bad: $kb kb (or more) leaked"
+fi