Fix NPE discovered by running bpf kselftest #31939

Job	Run time
set-matrix	2s
x86_64-gcc / build-release	0s
x86_64-llvm-17 / build / build for x86_64 with llvm-17	4m 3s
x86_64-llvm-17 / build-release / build for x86_64 with llvm-17-O2	3m 50s
x86_64-gcc / build / build for x86_64 with gcc	3m 45s
x86_64-llvm-18 / build / build for x86_64 with llvm-18	4m 4s
x86_64-llvm-18 / build-release / build for x86_64 with llvm-18-O2	3m 49s
x86_64-gcc / veristat-kernel	0s
x86_64-gcc / veristat-meta	0s
x86_64-gcc / test	0s
x86_64-llvm-17 / test	0s
x86_64-llvm-17 / veristat-meta	0s
x86_64-llvm-17 / veristat-kernel	0s
x86_64-llvm-18 / test	0s
x86_64-llvm-18 / veristat-kernel	0s
x86_64-llvm-18 / veristat-meta	0s
	19m 33s

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