hush: fix 'eval ""' handling

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/shell/ash_test/ash-misc/eval2.right b/shell/ash_test/ash-misc/eval2.right
new file mode 100644
index 0000000..a7ce6cc
--- /dev/null
+++ b/shell/ash_test/ash-misc/eval2.right
@@ -0,0 +1,3 @@
+Zero:0
+Zero:0
+Zero:0