[turbofan] Better handling of empty type in simplified lowering.

test/mjsunit/compiler/regress-625558.js

Index: test/mjsunit/compiler/regress-625558.js
diff --git a/test/mjsunit/regress/regress-opt-typeof-null.js b/test/mjsunit/compiler/regress-625558.js
similarity index 68%
copy from test/mjsunit/regress/regress-opt-typeof-null.js
copy to test/mjsunit/compiler/regress-625558.js
index e4721a18c5e0fb95a3b7cb323f229de9f605b64a..5d6b372632abd0adbeffe24f31e2abe60e9acbff 100644
--- a/test/mjsunit/regress/regress-opt-typeof-null.js
+++ b/test/mjsunit/compiler/regress-625558.js
@@ -4,9 +4,11 @@
 
 // Flags: --allow-natives-syntax
 
+for (var global = 0; global <= 256; global++) { }
+
 function f() {
-  return typeof null === "object";
-};
+  global = "luft";
+  global += ++global;
+}
 
-%OptimizeFunctionOnNextCall(f);
-assertTrue(f());
+f();