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
}
        AExpression userConditionNode = userForNode.getConditionNode();
        SBlock userBlockNode = userForNode.getBlockNode();
        boolean continuous = false;
        if (userConditionNode != null) {
            semanticScope.setCondition(userConditionNode, Read.class);
            semanticScope.putDecoration(userConditionNode, new TargetType(boolean.class));
            checkedVisit(userConditionNode, semanticScope);
            decorateWithCast(userConditionNode, semanticScope);
            if (userConditionNode instanceof EBooleanConstant bc) {
                continuous = bc.getBool();
                if (continuous == false) {
                    throw userForNode.createError(new IllegalArgumentException("extraneous for loop"));
                }
                if (userBlockNode == null) {
                    throw userForNode.createError(new IllegalArgumentException("no paths escape from for loop"));
                }
            }
        } else {
            continuous = true;
        }
        AExpression userAfterthoughtNode = userForNode.getAfterthoughtNode();
        if (userAfterthoughtNode != null) {
            checkedVisit(userAfterthoughtNode, semanticScope);
        }
        if (userBlockNode != null) {
            semanticScope.setCondition(userBlockNode, BeginLoop.class);
            semanticScope.setCondition(userBlockNode, InLoop.class);
            visit(userBlockNode, semanticScope);
            if (semanticScope.getCondition(userBlockNode, LoopEscape.class)