Device automatically paired although joining was disabled

When I tried to pair a Hue Tap with my Hue Bridge today, I noticed shortly after in ZigBee2MQTT that the device was also paired here, although Allow Join was disabled. How could this happen? I noticed the following in the log:

(node:17) UnhandledPromiseRejectionWarning: TypeError [ERR_INVALID_ARG_TYPE]: The "data" argument must be of type string or an instance of Buffer, TypedArray, or DataView. Received undefined

at Cipheriv.update (internal/crypto/cipher.js:155:11)

at GreenPower.encryptSecurityKey (/app/node_modules/zigbee-herdsman/dist/controller/greenPower.js:50:34)

at GreenPower.<anonymous> (/app/node_modules/zigbee-herdsman/dist/controller/greenPower.js:57:34)

at (<anonymous>)

at /app/node_modules/zigbee-herdsman/dist/controller/greenPower.js:8:71

at new Promise (<anonymous>)

at __awaiter (/app/node_modules/zigbee-herdsman/dist/controller/greenPower.js:4:12)

at GreenPower.onZclGreenPowerData (/app/node_modules/zigbee-herdsman/dist/controller/greenPower.js:54:16)

at Controller.<anonymous> (/app/node_modules/zigbee-herdsman/dist/controller/controller.js:405:37)

at (<anonymous>)

(node:17) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see (rejection id: 1)

(node:17) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the         future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

Pairing with the Hue Bridge also took quite a long time, probably because the device paired with Z2M first. But it seems that it was paired correctly with the Hue Bridge afterwards and no more status messages arrive via Z2M when pressing a button