[diag] Handle errors of `TransmitPacket()` #13

Job	Run time
channel-manager-csl	3m 12s
expects	31m 2s
packet-verification-1-1-on-1-4	10m 36s
packet-verification-low-power	9m 0s
thread-1-4-gcc-m32	11m 38s
thread-1-4-gcc-m64	11m 26s
thread-1-4-posix	9m 32s
thread-1-4-clang-m32	10m 8s
thread-1-4-clang-m64	9m 31s
upload-coverage	25s
	1h 46m 30s

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