Fix #14796: FP assertWithSideEffect for member functions without definition #19910

Job	Run time
build_cmake (ubuntu:24.04, true, true)	5m 15s
build_make (ubuntu:25.10)	4m 0s
build_make (alpine:3.23)	5m 56s
build_make (ubuntu:24.04)	3m 41s
build_cmake (ubuntu:25.10, true, true)	5m 9s
build_cmake (alpine:3.23, false, false)	3m 33s
	27m 34s

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