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
SBlock userElseBlockNode = userIfElseNode.getElseBlockNode();
        if (userElseBlockNode == null) {
            throw userIfElseNode.createError(new IllegalArgumentException("extraneous else block."));
        }
        semanticScope.replicateCondition(userIfElseNode, userElseBlockNode, LastSource.class);
        semanticScope.replicateCondition(userIfElseNode, userElseBlockNode, InLoop.class);
        semanticScope.replicateCondition(userIfElseNode, userElseBlockNode, LastLoop.class);
        visit(userElseBlockNode, semanticScope.newLocalScope());
        if (semanticScope.getCondition(userIfBlockNode, MethodEscape.class)
            && semanticScope.getCondition(userElseBlockNode, MethodEscape.class)) {
            semanticScope.setCondition(userIfElseNode, MethodEscape.class);
        }
        if (semanticScope.getCondition(userIfBlockNode, LoopEscape.class)
            && semanticScope.getCondition(userElseBlockNode, LoopEscape.class)) {
            semanticScope.setCondition(userIfElseNode, LoopEscape.class);
        }
        if (semanticScope.getCondition(userIfBlockNode, AllEscape.class)
            && semanticScope.getCondition(userElseBlockNode, AllEscape.class)) {
            semanticScope.setCondition(userIfElseNode, AllEscape.class);
        }
        if (semanticScope.getCondition(userIfBlockNode, AnyContinue.class)
            || semanticScope.getCondition(userElseBlockNode, AnyContinue.class)) {
            semanticScope.setCondition(userIfElseNode, AnyContinue.class);
        }
        if (semanticScope.getCondition(userIfBlockNode, AnyBreak.class) || semanticScope.getCondition(userElseBlockNode, AnyBreak.class)) {
            semanticScope.setCondition(userIfElseNode, AnyBreak.class);
        }
    }
    /**
     * Visits a while statement with error checking for an extraneous loop.