User can navigate chapter 0 or more than the current chapter

[adreeeyan]

Steps:

1. Open any novel
2. Open chapter 1

   Reader is shown

3. Navigate to previous chapter (e.g. tap screen and tap previous button)

   Endless loading screen

Expected result: No previous button should be shown

Other steps:

1. Open any novel
2. Open last chapter

   Reader is shown

3. Navigate to next chapter (e.g. tap screen and tap next button)

   Endless loading screen

Expected result: App should tell the user that there is no more next chapter available