I got an unexpected internal NPE when playing with this script.

```
POST _scripts/painless/_execute
{
  "script": {
    "source": """
    return /[^\w]+/.split('abc   def higkln').toArray(String[]::new)
    """
  }
}
```
```
{
  "error" : {
    "root_cause" : [
      {
        "type" : "script_exception",
        "reason" : "compile error",
        "script_stack" : [ ],
        "script" : "\n    return /[^\\w]+/.split('abc   def higkln').toArray(String[]::new)\n    ",
        "lang" : "painless"
      }
    ],
    "type" : "script_exception",
    "reason" : "compile error",
    "script_stack" : [ ],
    "script" : "\n    return /[^\\w]+/.split('abc   def higkln').toArray(String[]::new)\n    ",
    "lang" : "painless",
    "caused_by" : {
      "type" : "null_pointer_exception",
      "reason" : "Cannot read field \"annotations\" because the return value of \"org.elasticsearch.painless.lookup.PainlessLookup.lookupPainlessClass(java.lang.Class)\" is null"
    }
  },
  "status" : 400
}

```
modules/lang-painless/src/main/java/org/elasticsearch/painless/phase/DefaultSemanticAnalysisPhase.java
}
        semanticScope.putDecoration(userNewArrayNode, new ValueType(valueType));
    }
    /**
     * Visits a new obj expression which creates a new object and calls its constructor.
     * Checks: type validation
     */
    @Override
    public void visitNewObj(ENewObj userNewObjNode, SemanticScope semanticScope) {
        String canonicalTypeName = userNewObjNode.getCanonicalTypeName();
        List<AExpression> userArgumentNodes = userNewObjNode.getArgumentNodes();
        int userArgumentsSize = userArgumentNodes.size();
        if (semanticScope.getCondition(userNewObjNode, Write.class)) {
            throw userNewObjNode.createError(
                new IllegalArgumentException(
                    "invalid assignment cannot assign a value to new object with constructor "
                        + "["
                        + canonicalTypeName
                        + "/"
                        + userArgumentsSize
                        + "]"
                )
            );
        }
        ScriptScope scriptScope = semanticScope.getScriptScope();
        Class<?> valueType = scriptScope.getPainlessLookup().canonicalTypeNameToType(canonicalTypeName);
        if (valueType == null) {
            throw userNewObjNode.createError(new IllegalArgumentException("Not a type [" + canonicalTypeName + "]."));
        }
        PainlessConstructor constructor = scriptScope.getPainlessLookup().lookupPainlessConstructor(valueType, userArgumentsSize);