message: Allow null to be return from the definition request.
diff: @@ -985,9 +985,9 @@ export interface SignatureHelp {
  /**
  * The definition of a symbol represented as one or many [locations](#Location).
  * For most programming languages there is only one location at which a symbol is
  - * defined.
  + * defined. If no definition can be found `null` is returned.
  */
  -export type Definition = Location | Location[];
  +export type Definition = Location | Location[] | null;
  /**
  * Value-object that contains additional information when
  