libphoenx/scanf: Fix SEGFAULT caused by invalid processing of %n #1126

Job	Run time
call-ci / build (armv7a7-imx6ull-evk)	1m 8s
call-ci / build (armv7a9-zynq7000-qemu)	1m 17s
call-ci / build (armv7a9-zynq7000-zedboard)	1m 3s
call-ci / build (armv7a9-zynq7000-zturn)	59s
call-ci / build (armv7m4-stm32l4x6-nucleo)	1m 6s
call-ci / build (armv7m7-imxrt105x-evk)	1m 13s
call-ci / build (armv7m7-imxrt106x-evk)	1m 19s
call-ci / build (armv7m7-imxrt117x-evk)	1m 23s
call-ci / build (host-generic-pc)	55s
call-ci / build (ia32-generic-pc)	1m 3s
call-ci / build (ia32-generic-qemu)	1m 2s
call-ci / build (riscv64-generic-qemu)	59s
call-ci / build (riscv64-generic-spike)	1m 11s
call-ci / build (sparcv8leon3-gr716-mini)	53s
call-ci / test HW (armv7a7-imx6ull-evk)	5m 30s
call-ci / test HW (armv7m7-imxrt106x-evk)	2m 41s
call-ci / test EMU (armv7a9-zynq7000-qemu)	10m 28s
call-ci / test HW (armv7m7-imxrt117x-evk)	2m 53s
call-ci / test EMU (host-generic-pc)	56s
call-ci / test HW (armv7a9-zynq7000-zedboard)	6m 12s
call-ci / test EMU (ia32-generic-qemu)	6m 50s
call-ci / test HW (armv7m4-stm32l4x6-nucleo)	10m 50s
call-ci / test EMU (riscv64-generic-qemu)	5m 51s
call-ci / tests-summary	32s
call-ci / send-notification	0s
	1h 8m 14s

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