fix null check

src/server/routes/apiv3/slack-integration-settings.js

@@ -121,7 +121,7 @@ module.exports = (crowi) => {
 
     // retrieve settings
     const settings = {};
-    if (currentBotType === null) {
+    if (currentBotType == null) {
       settings.slackSigningSecretEnvVars = configManager.getConfigFromEnvVars('crowi', 'slackbot:signingSecret');
       settings.slackBotTokenEnvVars = configManager.getConfigFromEnvVars('crowi', 'slackbot:token');
       settings.slackSigningSecret = null;