Popups throughout KOReader cause crashes when Kochess is installed

[renpenguin]

Describe the bug
Interacting with any popups, such as confirmation prompts, book options, "restart?" prompts, plugin disable confirmations, causes KOReader to crash and the default e-book interface to re-appear.

This only occurs when kochess is installed. Uninstalling resolved the issue.

To Reproduce

1. With KOReader open, go to the file browser
2. Press and hold on any book
3. Attempt to select any option in the popup

This occured both with the ZenUI and SimpleUI plugins.

Crash Log

(Click to reveal)

---------------------------------------------
                launching...
  _  _____  ____                _
 | |/ / _ \|  _ \ ___  __ _  __| | ___ _ __
 | ' / | | | |_) / _ \/ _` |/ _` |/ _ \ '__|
 | . \ |_| |  _ <  __/ (_| | (_| |  __/ |
 |_|\_\___/|_| \_\___|\__,_|\__,_|\___|_|

 It's a scroll... It's a codex... It's KOReader!

 [*] Current time: 07/21/26-20:28:12
has monolibtic? no (libs/libkoreader-monolibtic.so: cannot open shared object file: No such file or directory)
lib_search_path: libs/?
lib_basic_format: lib%s.so
lib_version_format: lib%s.so.%s
 [*] Version: v2026.03

ffi.load: rt.so.1 (RTLD_GLOBAL)
ffi.findlib: utf8proc [3]
ffi.load: libs/libutf8proc.so.3
ffi.findlib: blitbuffer
ffi.load: libs/libblitbuffer.so
ffi.findlib: archive [13]
ffi.load: libs/libarchive.so.13
ffi.findlib: fbink_input [1]
ffi.load: libs/libfbink_input.so.1
[FBInk] /dev/input/event0: `max77696-onkey` = KEY | POWER_BUTTON
[FBInk] /dev/input/event1: `cyttsp4_mt` = TOUCHSCREEN
[ko-input] Forked off fake event generator (pid: 12469)
07/21/26-20:28:13 INFO  initializing for device KindlePaperWhite3 
07/21/26-20:28:13 INFO  framebuffer resolution: {
  h = 1448,
  w = 1072
} --[[table: 0x40490788]] 
ffi.findlib: wrap-mupdf
ffi.load: libs/libwrap-mupdf.so
ffi.findlib: sqlite3 [0]
ffi.load: libs/libsqlite3.so.0
ffi.findlib: freetype [6]
ffi.load: libs/libfreetype.so.6
ffi.findlib: harfbuzz [0]
ffi.load: libs/libharfbuzz.so.0
ffi.findlib: zstd [1]
ffi.load: libs/libzstd.so.1
07/21/26-20:28:14 INFO  Looking for plugins in directory: plugins 
ffi.findlib: leptonica [6]
ffi.load: libs/libleptonica.so.6
ffi.findlib: k2pdfopt [2]
ffi.load: libs/libk2pdfopt.so.2
07/21/26-20:28:15 INFO  KOCHESS: Plugin path detected: plugins/kochess.koplugin/ 
07/21/26-20:28:15 INFO  KOCHESS: Detected architecture: armv7l 
07/21/26-20:28:15 INFO  KOCHESS: Installing icons 
07/21/26-20:28:15 INFO  KOCHESS: data_dir  = . 
07/21/26-20:28:15 INFO  KOCHESS: src_dir   = plugins/kochess.koplugin/icons 
07/21/26-20:28:15 INFO  KOCHESS: dest_dir  = ./resources/icons/chess 
CRE: font NotoSerifKR regular: updated weight from 500 to 400
CRE: font NotoSerifKR bold: updated weight from 900 to 700
CRE: font PMN Caecilia LT regular: updated weight from 500 to 400
CRE: font NotoSansKR bold: updated weight from 900 to 700
./luajit: frontend/ui/widget/button.lua:406: attempt to index field 'background' (a nil value)
stack traceback:
	frontend/ui/widget/button.lua:406: in function '_doFeedbackHighlight'
	frontend/ui/widget/button.lua:461: in function 'handleEvent'
	frontend/ui/widget/container/inputcontainer.lua:269: in function 'handleEvent'
	frontend/ui/widget/container/widgetcontainer.lua:83: in function 'propagateEvent'
	frontend/ui/widget/container/widgetcontainer.lua:101: in function 'handleEvent'
	frontend/ui/widget/container/widgetcontainer.lua:83: in function 'propagateEvent'
	frontend/ui/widget/container/widgetcontainer.lua:101: in function 'handleEvent'
	frontend/ui/widget/container/widgetcontainer.lua:83: in function 'propagateEvent'
	frontend/ui/widget/container/widgetcontainer.lua:101: in function 'handleEvent'
	frontend/ui/widget/container/widgetcontainer.lua:83: in function 'propagateEvent'
	frontend/ui/widget/container/widgetcontainer.lua:101: in function 'handleEvent'
	...
	frontend/ui/widget/container/widgetcontainer.lua:101: in function 'handleEvent'
	frontend/ui/widget/container/widgetcontainer.lua:83: in function 'propagateEvent'
	frontend/ui/widget/container/widgetcontainer.lua:101: in function 'handleEvent'
	frontend/ui/uimanager.lua:910: in function 'sendEvent'
	frontend/ui/uimanager.lua:53: in function '__default__'
	frontend/ui/uimanager.lua:1437: in function 'handleInputEvent'
	frontend/ui/uimanager.lua:1537: in function 'handleInput'
	frontend/ui/uimanager.lua:1581: in function 'run'
	./reader.lua:295: in main chunk
	[C]: at 0x00013eb1
lipc-wait-event exited normally with status: 0

Device details

• Device/OS: Kindle PW7 - WinterBreak2
• KOReader version: 2026.03
• App Version: 2.2.4
• Language: en

[renpenguin]

Pull request #12 offers a fix to this