bpf: Fix mprog detachment for empty mprog entry #23221

Job	Run time
set-matrix	1s
build for x86_64 with gcc	3m 44s
build for x86_64 with llvm-16	3m 12s
build for aarch64 with gcc	4m 19s
build for s390x with gcc	12m 56s
veristat	1m 55s
test_progs on x86_64 with gcc	4m 1s
test_progs_parallel on x86_64 with gcc	2m 37s
test_progs_no_alu32 on x86_64 with gcc	3m 45s
test_progs_no_alu32_parallel on x86_64 with gcc	2m 31s
test_maps on x86_64 with gcc	2m 47s
test_verifier on x86_64 with gcc	1m 44s
test_progs on x86_64 with llvm-16	4m 26s
test_progs_parallel on x86_64 with llvm-16	3m 3s
test_progs_no_alu32 on x86_64 with llvm-16	3m 45s
test_progs_no_alu32_parallel on x86_64 with llvm-16	2m 45s
test_maps on x86_64 with llvm-16	2m 55s
test_verifier on x86_64 with llvm-16	1m 49s
test_progs on aarch64 with gcc	5m 15s
test_progs_parallel on aarch64 with gcc	3m 7s
test_progs_no_alu32 on aarch64 with gcc	4m 39s
test_progs_no_alu32_parallel on aarch64 with gcc	2m 58s
test_maps on aarch64 with gcc	3m 19s
test_verifier on aarch64 with gcc	1m 38s
test_progs on s390x with gcc	31m 28s
test_progs_no_alu32 on s390x with gcc	18m 35s
test_maps on s390x with gcc	54m 51s
test_verifier on s390x with gcc	6m 13s
	3h 14m 18s

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