Fix #14796: FP assertWithSideEffect for member functions without definition #20295

Job	Run time
build_cmake (alpine:3.23, false, false)	4m 28s
build_cmake (ubuntu:24.04, true, true)	3m 11s
build_make (ubuntu:25.10)	3m 37s
build_make (ubuntu:24.04)	3m 19s
build_make (alpine:3.23)	4m 54s
build_cmake (ubuntu:25.10, true, true)	3m 2s
	22m 31s

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