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.setCondition(userRightNode, Read.class);
        checkedVisit(userRightNode, semanticScope);
        Class<?> rightValueType = semanticScope.getDecoration(userRightNode, ValueType.class).valueType();
        Class<?> valueType;
        Class<?> binaryType;
        Class<?> shiftType = null;
        if (operation == Operation.FIND || operation == Operation.MATCH) {
            semanticScope.putDecoration(userLeftNode, new TargetType(String.class));
            semanticScope.putDecoration(userRightNode, new TargetType(Pattern.class));
            decorateWithCast(userLeftNode, semanticScope);
            decorateWithCast(userRightNode, semanticScope);
            binaryType = boolean.class;
            valueType = boolean.class;
        } else {
            if (operation == Operation.MUL || operation == Operation.DIV || operation == Operation.REM) {
                binaryType = AnalyzerCaster.promoteNumeric(leftValueType, rightValueType, true);
            } else if (operation == Operation.ADD) {
                binaryType = AnalyzerCaster.promoteAdd(leftValueType, rightValueType);
            } else if (operation == Operation.SUB) {
                binaryType = AnalyzerCaster.promoteNumeric(leftValueType, rightValueType, true);
            } else if (operation == Operation.LSH || operation == Operation.RSH || operation == Operation.USH) {
                binaryType = AnalyzerCaster.promoteNumeric(leftValueType, false);
                shiftType = AnalyzerCaster.promoteNumeric(rightValueType, false);
                if (shiftType == null) {
                    binaryType = null;
                }
            } else if (operation == Operation.BWOR || operation == Operation.BWAND) {
                binaryType = AnalyzerCaster.promoteNumeric(leftValueType, rightValueType, false);
            } else if (operation == Operation.XOR) {
                binaryType = AnalyzerCaster.promoteXor(leftValueType, rightValueType);