fix a corner case in #1530 (#1552)

1 files changed, 6 insertions, 4 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 35459006..7eead2c1 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -2760,10 +2760,12 @@ merge(Compressor.prototype, {
             }
         }
         if (exp instanceof AST_Function) {
-            if (exp.body[0] instanceof AST_Return
-                && exp.body[0].value.is_constant()) {
-                var args = self.args.concat(exp.body[0].value);
-                return AST_Seq.from_array(args).transform(compressor);
+            if (exp.body[0] instanceof AST_Return) {
+                var value = exp.body[0].value;
+                if (!value || value.is_constant()) {
+                    var args = self.args.concat(value || make_node(AST_Undefined, self));
+                    return AST_Seq.from_array(args).transform(compressor);
+                }
             }
             if (compressor.option("side_effects")) {
                 if (!AST_Block.prototype.has_side_effects.call(exp, compressor)) {