message: Add missing null types
diff: @@ -50,7 +50,7 @@ export function codegen(contract: Contract) {
  options?: {
  filter?: object;
  fromBlock?: BlockType;
  - topics?: string[];
  + topics?: (null|string)[];
  },
  cb?: Callback<EventLog>
  ) => EventEmitter;
  @@ -112,7 +112,7 @@ function generateEvents(event: EventDeclaration) {
  options?: {
  filter?: object;
  fromBlock?: BlockType;
  - topics?: string[];
  + topics?: (null|string)[];
  },
  cb?: Callback<EventLog>): EventEmitter;
  `;
  