[Interpreter] Ensure that implicit return undefined is generated.

test/cctest/interpreter/test-bytecode-generator.cc

Index: test/cctest/interpreter/test-bytecode-generator.cc
diff --git a/test/cctest/interpreter/test-bytecode-generator.cc b/test/cctest/interpreter/test-bytecode-generator.cc
index c62e5efff9f2a93756f4022d64469b85d4f1f252..25a71488936bab3c9ecb5f1454990395a02bbd7c 100644
--- a/test/cctest/interpreter/test-bytecode-generator.cc
+++ b/test/cctest/interpreter/test-bytecode-generator.cc
@@ -79,6 +79,7 @@ TEST(PrimitiveReturnStatements) {
   BytecodeGeneratorHelper helper;
 
   ExpectedSnippet<void*> snippets[] = {
+      {"", 0, 1, 2, {B(LdaUndefined), B(Return)}, 0},
       {"return;", 0, 1, 2, {B(LdaUndefined), B(Return)}, 0},
       {"return null;", 0, 1, 2, {B(LdaNull), B(Return)}, 0},
       {"return true;", 0, 1, 2, {B(LdaTrue), B(Return)}, 0},