Kolab notes app crashes after drawing a couple of drawings in a note/book

Project Information: https://github.com/konradrenner/kolabnotes-android

Project Name : Kolab Notes

Expected behavior :

After creating a note in the Kolab notes app in a particular way, the app was expected to open the note after saving it. The particular way which I'm talking about is explained as: When I give the name to the note and then draw something by pressing the drawing option and save the drawing and when I add another drawing to it and save the note. After saving the note and then when I try to open the note the app is expected to open the note/book.

Actual behavior :

When I follow the above mentioned procedure of making a drawing and saving it and then adding another drawing to the note and then saving it. After saving the note/book, when we click on the note/book to open it, the app crashes.

How to reproduce:

Install the app, Kolab notes, to your phone from Fdroid.
Open the app and click on the pencil icon to start creating a note/book.
Write the name and summary in the first two boxes.
Press the white screen for more options.
Click on the drawing option to draw your drawing.
Now press the tick icon to save your drawing.
To draw another drawing in your note, press the screen again to get the drawing option.
Now after completing the drawing save it and save the note.
Now try to open the note you just created.
The app will crash.
Android 7.0
App version 3.1.3

Proof of work done:

https://github.com/syedubair

konradrenner / kolabnotes-android