0.96.2: Cannot navigate pages in TIFF after saving a page

[bar_foo]

XnView: MP 0.96.2 4 bit
OS: Windows 10 64bit

After using Save As on a page in a multipage TIFF and saving that page as a PNG, can no longer navigate pages in the TIFF

Effect: XnViewMP still displays the page, but the navigation buttons in the toolbar don't work. The Previous Page button appears enabled but clicking it does nothing and the Next Page button is disabled.

To reproduce:
1. Open a multipage TIFF file
2. Use the Next Page to navigate to the intended page
3. Use Save As to save the page as a PNG file
4. Attempt to navigate further

Actual behaviour (bug): Page navigation buttons do not work, only Previous Page is enabled

Expected behaviour: Page navigation buttons are enabled and functional

Notes:
Navigation is restored if the file is Reloaded (Ctrl-R), but returned to the first page
This does not happen when using Export rather than Save As

[xnview]

if you use 'settings>use output filename after save as', output file becomes the current image file

[Motoroller]

Hello!

I open in XnView MP Windows (ver. 0.97.0 64 bits sep 23 2020) and XnView MP Linux (ver. 0.97.0 64 bits sep 24 2020) 2 pages test TIFF-file:

https://drive.google.com/file/d/16MBu-U ... p=sharing

XnView MP -> Info -> Image -> Images/frames count 2

Button press 90 left rotates the image, <ctrl+S> keeps -> The file <home/usr/GoogleDrive/Temp/img05903.tif> already exists! Do you want to overwrite? -> Ok.

File changes: Info -> Image -> Images/frames count 1

XnView MP turns a multi-page TIFF-file into a single page.

In XnView Classic, the same algorithm does the right thing, saves the modified page of a multi-page TIFF-file to a multi-page TIFF-file.

I ask for your help in solving the problem.

[xnview]

In XnView Classic, the same algorithm does the right thing, saves the modified page of a multi-page TIFF-file to a multi-page TIFF-file.

Currently only first frame is saved... but i'll add same support