[diag] Handle errors of `TransmitPacket()` #11

Job	Run time
packet-verification-low-power	8m 44s
thread-1-4-gcc-m32	11m 27s
thread-1-4-gcc-m64	11m 32s
thread-1-4-clang-m32	9m 45s
thread-1-4-clang-m64	9m 42s
channel-manager-csl	3m 22s
expects	27m 52s
packet-verification-1-1-on-1-4	11m 1s
thread-1-4-posix	9m 41s
upload-coverage	0s
	1h 43m 6s

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