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
&& setter != null
                                    && (getter.typeParameters().get(0).equals(setter.typeParameters().get(0)) == false
                                        || getter.returnType().equals(setter.typeParameters().get(1)) == false)) {
                                    throw userDotNode.createError(new IllegalArgumentException("Shortcut argument types must match."));
                                }
                                if ((read == false || getter != null) && (write == false || setter != null)) {
                                    valueType = setter != null ? setter.typeParameters().get(1) : getter.returnType();
                                } else {
                                    throw userDotNode.createError(
                                        new IllegalArgumentException("Illegal list shortcut for type [" + prefixCanonicalTypeName + "].")
                                    );
                                }
                                if (getter != null) {
                                    semanticScope.putDecoration(userDotNode, new GetterPainlessMethod(getter));
                                }
                                if (setter != null) {
                                    semanticScope.putDecoration(userDotNode, new SetterPainlessMethod(setter));
                                }
                                semanticScope.setCondition(userDotNode, ListShortcut.class);
                            }
                        }
                        if (valueType == null) {
                            if (prefixValueType != null) {
                                throw userDotNode.createError(
                                    new IllegalArgumentException(
                                        "field [" + prefixValueType.getValueCanonicalTypeName() + ", " + index + "] not found"
                                    )
                                );
                            } else {
                                throw userDotNode.createError(