fcup-smsend[mult]: fix buglet in K&R C NULL pointer passing The only 100% safe way to pass a NULL pointer as a function argument in K&R C is to cast 0 to a pointer type; failing to do so may cause mysterious bugs (invalid stack frames or garbage in argument registers) on 64-bit machines. This issue has already been fixed in most of FC host tools, but I just found some missed spots: passing of NULL UDH to PDU encoding functions in fcup-smsend[mult] in the case of single (not concatenated) SMS.

	.text
	.globl	_entry
_entry:
	.code	16
	bx	pc
	nop

	.code	32
	stmfd	sp!, {r0-r12,lr}
	mrs	r0, CPSR
	mov	r1, sp
	/* supervisor mode, disable all interrupts */
	msr	CPSR_c, #0xd3
	ldr	sp, =stack_bottom
	/* save entry SP and CPSR */
	ldr	r2, =lldbg_entry_cpsr
	str	r0, [r2]
	ldr	r2, =lldbg_entry_sp
	str	r1, [r2]
	b	main