Null Pointer Exception: E/AndroidRuntime: FATAL EXCEPTION: main Process: com.projeto.asminhasreceitas, PID: 8263

Question

I am getting a null pointer exception when I have the following class:

public Cursor getAllData(String s) {
        SQLiteDatabase db;
        db = this.getReadableDatabase();
        Cursor res = db.rawQuery("SELECT nome FROM " + TABELA_RECEITAS, null);
        if (res != null) {
            res.moveToFirst();
        }
        return res;
    }

I have also the following class that calls the first class:

 if (s != null) {
    Cursor cursor = myDB.getAllData(s);
            

Null Pointer Exception:

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.projeto.asminhasreceitas, PID: 8263
    java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.Cursor com.projeto.asminhasreceitas.helper.DBHelper.getAllData(java.lang.String)' on a null object reference
        at com.projeto.asminhasreceitas.ui.pesquisar.PesquisarFragment$1.onQueryTextSubmit(PesquisarFragment.java:63)
        at android.widget.SearchView.onSubmitQuery(SearchView.java:1570)
        at android.widget.SearchView.access$1000(SearchView.java:112)
        at android.widget.SearchView$7.onEditorAction(SearchView.java:1542)
        at android.widget.TextView.onEditorAction(TextView.java:7718)
        at com.android.internal.widget.EditableInputConnection.performEditorAction(EditableInputConnection.java:138)
        at com.android.internal.view.IInputConnectionWrapper.executeMessage(IInputConnectionWrapper.java:363)
        at com.android.internal.view.IInputConnectionWrapper$MyHandler.handleMessage(IInputConnectionWrapper.java:93)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:246)
        at android.app.ActivityThread.main(ActivityThread.java:8512)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:602)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1130)
I/Process: Sending signal. PID: 8263 SIG: 9

What I am doing wrong?