TypeError: undefined is not an Object after JDK-8240299

The following program is accepted by the version of nashorn that shipped in JDK 14, but rejected by the latest version of org.openjdk.nashorn.

My colleague Nicholas Burbaum found that the commit that changed this behaviour is https://github.com/openjdk/nashorn/commit/9b87e5dadcabdf4965a278a4f090c0fffbbd60b7, and minimized the repro. He also mentioned that the fix might be to check against check against "obj" instead of "self".

```
import org.openjdk.nashorn.api.scripting.NashornScriptEngineFactory;

class NashornTest {

  public static void main(String[] args) throws Exception {
    String js = "var objectSetPrototypeOf = Object.setPrototypeOf; objectSetPrototypeOf({}, {});";
    new NashornScriptEngineFactory().getScriptEngine().eval(js);
  }
}
```

java -cp nashorn-core-15.3.jar:asm-9.2.jar:asm-util-9.2.jar:. NashornTest
Exception in thread "main" javax.script.ScriptException: TypeError: undefined is not an Object in <eval> at line number 1
at org.openjdk.nashorn.api.scripting.NashornScriptEngine.throwAsScriptException(NashornScriptEngine.java:463)
at org.openjdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:447)
at org.openjdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:399)
at org.openjdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:395)
at org.openjdk.nashorn.api.scripting.NashornScriptEngine.eval(NashornScriptEngine.java:151)
at java.scripting/javax.script.AbstractScriptEngine.eval(AbstractScriptEngine.java:264)
at NashornTest.main(NashornTest.java:7)
Caused by: <eval>:1 TypeError: undefined is not an Object
at org.openjdk.nashorn.internal.runtime.ECMAErrors.error(ECMAErrors.java:57)
at org.openjdk.nashorn.internal.runtime.ECMAErrors.typeError(ECMAErrors.java:212)
at org.openjdk.nashorn.internal.runtime.ECMAErrors.typeError(ECMAErrors.java:184)
at org.openjdk.nashorn.internal.runtime.ECMAErrors.typeError(ECMAErrors.java:171)
at org.openjdk.nashorn.internal.objects.Global.checkObjectCoercible(Global.java:2391)
at org.openjdk.nashorn.internal.objects.NativeObject.setPrototypeOf(NativeObject.java:201)
at org.openjdk.nashorn.internal.scripts.Script$\^eval\_/0x0000000800c8e840.:program(<eval>:1)
at org.openjdk.nashorn.internal.runtime.ScriptFunctionData.invoke(ScriptFunctionData.java:646)
at org.openjdk.nashorn.internal.runtime.ScriptFunction.invoke(ScriptFunction.java:513)
at org.openjdk.nashorn.internal.runtime.ScriptRuntime.apply(ScriptRuntime.java:520)
at org.openjdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:442)
... 5 more