title: Problem with select in redux-saga. Error: call: argument of type {context, fn} has undefined or null `fn`
body: <p>After looking through some answers to similar questions here, I just can't get my selector to work. Here's my selector.js:</p>
  
  <pre><code>export const getButtonStatus = state =&gt; state.buttonStatus;
  </code></pre>
  
  <p>(That's the entirety of the file. I don't know if I have to import anything into it. Didn't seem like it from looking at other answers I've seen here.)</p>
  
  <p>and here's what I'm where I'm trying to access the selector in my saga:</p>
  
  <pre><code>import { takeLatest, call, put, select } from "redux-saga/effects";
  import { getButtonStatus } from "./selector.js";
  ...
  export function* watcherSaga() {
    yield takeLatest("get-tweets", workerSaga);
  }
  
  function* workerSaga() {
    try {
      const buttonStatus = yield select(getButtonStatus);
      const response = yield call(getTweets(buttonStatus));
      const tweets = response.tweets;
      yield put({
        type: "tweets-received-async",
        tweets: tweets,
        nextTweeter: response.nextTweeter
      });
    } catch (error) {
      console.log("error = ", error);
      yield put({ type: "error", error });
    }
  }
  ...
  </code></pre>
  
  <p>Here's the error I'm receiving:</p>
  
  <pre><code> Error: call: argument of type {context, fn} has undefined or null `fn`
  </code></pre>
  
  <p>I'm new to Saga. Can anyone tell me what I'm doing wrong?</p>