A screen shot of compressed blocks is unhelpful.
Expand them all.
In addition to what @ABG has already said (collapsed blocks are unreadable), what I can see from your blocks is that you load a list from a kind of elements, but you select (pick) from another one:
As if you want to pick an apple from a chest of pears.... 
What sh
ould I do?
The following should solve the list pointer error
but I feel that the sequence of initialization of the BLE connection is not 100% correct (i.e. start/stop scanning, permission granting, etc.)
To this purpose I suggest you to take a look to @ABG 's FAQ here:
In other words, before attempting the communication with your own written app, I suggest you to try a ready made one (retrieved from the forum) and only after you're done successfully with that, you can implement yours.
Another solution is: you can use the Serial Bluetooth Terminal (SBT) app, free from Playstore to check if the ESP32 side is working correctly in transmitting and receiving data to your Android device.
In effect, by running the SBT on the Android device (phone or tablet, whichever you have), you are free from doubts on Android side, and you can focus your attention to the ESP32 side only and, once you are sure that the ESP32 is working fine, you can move your attention to your app.
Best wishes.