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
returnType = def.class;
            
            typeParameters = new ArrayList<>(canonicalTypeNameParameters.size());
            for (String type : canonicalTypeNameParameters) {
                if (type == null) {
                    typeParameters.add(def.class);
                } else {
                    Class<?> typeParameter = scriptScope.getPainlessLookup().canonicalTypeNameToType(type);
                    if (typeParameter == null) {
                        throw userLambdaNode.createError(new IllegalArgumentException("cannot resolve type [" + type + "]"));
                    }
                    typeParameters.add(typeParameter);
                }
            }
        } else {
            
            interfaceMethod = scriptScope.getPainlessLookup().lookupFunctionalInterfacePainlessMethod(targetType.targetType());
            if (interfaceMethod == null) {
                throw userLambdaNode.createError(
                    new IllegalArgumentException(
                        "Cannot pass lambda to " + "[" + targetType.getTargetCanonicalTypeName() + "], not a functional interface"
                    )
                );
            }
            
            if (interfaceMethod.typeParameters().size() != canonicalTypeNameParameters.size()) throw new IllegalArgumentException(
                "Incorrect number of parameters for ["
                    + interfaceMethod.javaMethod().getName()
                    + "] in ["
                    + targetType.getTargetCanonicalTypeName()