Searchable Spinner has caused my app to crash upon filtering the search loaded from firestore

Question

The data from my firestore database has been successfully loaded into my searchable spinner but upon trying to filter my items(i.e., upon searching through the searchable spinner), my app is getting crashed. CODE:

parties=new ArrayList<>();
    arrayAdapter = new ArrayAdapter<String>(cartActivity.this, android.R.layout.simple_list_item_1, parties);
    arrayAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    searchableSpinner.setAdapter(arrayAdapter);
    db.collection("/RootCollection/partyDocument/partyCollection")
            .get()
            .addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
                @Override
                public void onSuccess(QuerySnapshot queryDocumentSnapshots) {
                    for(QueryDocumentSnapshot documentSnapshot:queryDocumentSnapshots){
                            partyMaster pm=documentSnapshot.toObject(partyMaster.class);
                            parties.add(pm.getName());
                            arrayAdapter.notifyDataSetChanged();
                    }

                }
            });

The data is properly getting downloaded and visible in the searchable spinner but filtering the search results is crashing my app.

Error Logcat:

    --------- beginning of crash
06-11 15:58:42.244 8801-8801/com.example.user1.salesmanapp E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.user1.salesmanapp, PID: 8801
    java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference
        at android.widget.ArrayAdapter.getCount(ArrayAdapter.java:337)
        at android.widget.AdapterView.checkFocus(AdapterView.java:737)
        at android.widget.AdapterView$AdapterDataSetObserver.onInvalidated(AdapterView.java:860)
        at android.widget.AbsListView$AdapterDataSetObserver.onInvalidated(AbsListView.java:6749)
        at android.database.DataSetObservable.notifyInvalidated(DataSetObservable.java:50)
        at android.widget.BaseAdapter.notifyDataSetInvalidated(BaseAdapter.java:59)
        at android.widget.ArrayAdapter$ArrayFilter.publishResults(ArrayAdapter.java:546)
        at android.widget.Filter$ResultsHandler.handleMessage(Filter.java:282)
        at android.os.Handler.dispatchMessage(Handler.java:111)
        at android.os.Looper.loop(Looper.java:207)
        at android.app.ActivityThread.main(ActivityThread.java:5740)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:905)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:766)

The library which i have used for my searchableSpinner is

implementation 'com.toptoche.searchablespinner:searchablespinnerlibrary:1.3.1'

THANKS IN ADVANCE