sudoku: fix FS#7772: Sudoku: "Solve" Crash.
tree8fd87c07786ab78d3212349fa622e442d0722b43
drwxr-xr-x - apps
drwxr-xr-x - backdrops
drwxr-xr-x - bootloader
drwxr-xr-x - docs
drwxr-xr-x - firmware
drwxr-xr-x - flash
drwxr-xr-x - fonts
drwxr-xr-x - gdb
drwxr-xr-x - icons
drwxr-xr-x - manual
drwxr-xr-x - rbutil
drwxr-xr-x - tools
drwxr-xr-x - uisimulator
drwxr-xr-x - utils
drwxr-xr-x - wps