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
import org.elasticsearch.painless.symbol.Decorations.InLoop;
import org.elasticsearch.painless.symbol.Decorations.InstanceCapturingFunctionRef;
import org.elasticsearch.painless.symbol.Decorations.InstanceCapturingLambda;
import org.elasticsearch.painless.symbol.Decorations.InstanceType;
import org.elasticsearch.painless.symbol.Decorations.Internal;
import org.elasticsearch.painless.symbol.Decorations.IterablePainlessMethod;
import org.elasticsearch.painless.symbol.Decorations.LastLoop;
import org.elasticsearch.painless.symbol.Decorations.LastSource;
import org.elasticsearch.painless.symbol.Decorations.ListShortcut;
import org.elasticsearch.painless.symbol.Decorations.LoopEscape;
import org.elasticsearch.painless.symbol.Decorations.MapShortcut;
import org.elasticsearch.painless.symbol.Decorations.MethodEscape;
import org.elasticsearch.painless.symbol.Decorations.MethodNameDecoration;
import org.elasticsearch.painless.symbol.Decorations.Negate;
import org.elasticsearch.painless.symbol.Decorations.ParameterNames;
import org.elasticsearch.painless.symbol.Decorations.PartialCanonicalTypeName;
import org.elasticsearch.painless.symbol.Decorations.Read;
import org.elasticsearch.painless.symbol.Decorations.ReferenceDecoration;
import org.elasticsearch.painless.symbol.Decorations.ReturnType;
import org.elasticsearch.painless.symbol.Decorations.SemanticVariable;
import org.elasticsearch.painless.symbol.Decorations.SetterPainlessMethod;
import org.elasticsearch.painless.symbol.Decorations.ShiftType;
import org.elasticsearch.painless.symbol.Decorations.Shortcut;
import org.elasticsearch.painless.symbol.Decorations.StandardConstant;
import org.elasticsearch.painless.symbol.Decorations.StandardLocalFunction;
import org.elasticsearch.painless.symbol.Decorations.StandardPainlessClassBinding;
import org.elasticsearch.painless.symbol.Decorations.StandardPainlessConstructor;
import org.elasticsearch.painless.symbol.Decorations.StandardPainlessField;
import org.elasticsearch.painless.symbol.Decorations.StandardPainlessInstanceBinding;
import org.elasticsearch.painless.symbol.Decorations.StandardPainlessMethod;