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
if (shiftType == long.class) {
                        semanticScope.putDecoration(userRightNode, new TargetType(int.class));
                        semanticScope.setCondition(userRightNode, Explicit.class);
                    } else {
                        semanticScope.putDecoration(userRightNode, new TargetType(shiftType));
                    }
                } else {
                    semanticScope.putDecoration(userRightNode, new TargetType(binaryType));
                }
                decorateWithCast(userLeftNode, semanticScope);
                decorateWithCast(userRightNode, semanticScope);
            }
        }
        semanticScope.putDecoration(userBinaryNode, new ValueType(valueType));
        semanticScope.putDecoration(userBinaryNode, new BinaryType(binaryType));
        if (shiftType != null) {
            semanticScope.putDecoration(userBinaryNode, new ShiftType(shiftType));
        }
    }
    /**
     * Visits a boolean comp expression which covers boolean comparision operators.
     * Checks: type validation
     */
    @Override
    public void visitBooleanComp(EBooleanComp userBooleanCompNode, SemanticScope semanticScope) {
        Operation operation = userBooleanCompNode.getOperation();
        if (semanticScope.getCondition(userBooleanCompNode, Write.class)) {
            throw userBooleanCompNode.createError(
                new IllegalArgumentException(
                    "invalid assignment: cannot assign a value to " + operation.name + " operation " + "[" + operation.symbol + "]"