[PacketBufferHandle::IsNull] Missing null check after calling PacketB…

[vivien-apple]

…ufferHandle::CloneData in UserDirectedCommissioningClient

Problem

The packet buffer copy is not null checked.

[github-actions]

PR #25521: Size comparison from e324826 to a6e24e8

Decreases (1 build for cc32xx)

platform	target	config	section	e324826	a6e24e8	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL	.debug_info	20267068	2026706	-1	-0.0

Full report (1 build for cc32xx)

platform	target	config	section	e324826	a6e24e8	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL		0	0	0	0.0
			(read only)	644425	644425	0	0.0
			(read/write)	203688	203688	0	0.0
			.ARM.attributes	44	44	0	0.0
			.ARM.exidx	8	8	0	0.0
			.bss	197088	197088	0	0.0
			.comment	194	194	0	0.0
			.data	1480	1480	0	0.0
			.debug_abbrev	930235	930235	0	0.0
			.debug_aranges	87336	87336	0	0.0
			.debug_frame	300028	300028	0	0.0
			.debug_info	20267068	2026706	-1	-0.0
			.debug_line	2659698	2659698	0	0.0
			.debug_loc	2802749	2802749	0	0.0
			.debug_ranges	282952	282952	0	0.0
			.debug_str	3023892	3023892	0	0.0
			.ramVecs	780	780	0	0.0
			.resetVecs	64	64	0	0.0
			.rodata	105929	105929	0	0.0
			.shstrtab	232	232	0	0.0
			.stab	204	204	0	0.0
			.stabstr	441	441	0	0.0
			.stack	2048	2048	0	0.0
			.strtab	378514	378514	0	0.0
			.symtab	256624	256624	0	0.0
			.text	536372	536372	0	0.0