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
}
            } else {
                throw userBraceNode.createError(
                    new IllegalArgumentException("Illegal list shortcut for type [" + canonicalClassName + "].")
                );
            }
            semanticScope.setCondition(userBraceNode, ListShortcut.class);
        } else {
            throw userBraceNode.createError(
                new IllegalArgumentException(
                    "Illegal array access on type " + "[" + PainlessLookupUtility.typeToCanonicalTypeName(prefixValueType) + "]."
                )
            );
        }
        semanticScope.putDecoration(userBraceNode, new ValueType(valueType));
    }
    /**
     * Visits a call expression which is a method call with a qualifier (prefix).
     * Checks: type validation, method resolution
     */
    @Override
    public void visitCall(ECall userCallNode, SemanticScope semanticScope) {
        String methodName = userCallNode.getMethodName();
        List<AExpression> userArgumentNodes = userCallNode.getArgumentNodes();
        int userArgumentsSize = userArgumentNodes.size();
        if (semanticScope.getCondition(userCallNode, Write.class)) {
            throw userCallNode.createError(
                new IllegalArgumentException(
                    "invalid assignment: cannot assign a value to method call [" + methodName + "/" + userArgumentsSize + "]"
                )