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 userBinaryNode.createError(new IllegalStateException("unexpected binary operation [" + operation.name + "]"));
            }
            if (binaryType == null) {
                throw userBinaryNode.createError(
                    new ClassCastException(
                        "cannot apply the "
                            + operation.name
                            + " operator "
                            + "["
                            + operation.symbol
                            + "] to the types "
                            + "["
                            + PainlessLookupUtility.typeToCanonicalTypeName(leftValueType)
                            + "] and "
                            + "["
                            + PainlessLookupUtility.typeToCanonicalTypeName(rightValueType)
                            + "]"
                    )
                );
            }
            valueType = binaryType;
            if (binaryType == def.class || shiftType == def.class) {
                TargetType targetType = semanticScope.getDecoration(userBinaryNode, TargetType.class);
                if (targetType != null) {
                    valueType = targetType.targetType();
                }
            } else if (operation != Operation.ADD || binaryType != String.class) {
                semanticScope.putDecoration(userLeftNode, new TargetType(binaryType));
                if (operation == Operation.LSH || operation == Operation.RSH || operation == Operation.USH) {