ovsdb-idl: Fix use of uninitialized datum for graph consistency check. #3216

Job	Run time
dpdk gcc (ubuntu-24.04)	2m 37s
linux deb no dpdk	6m 11s
osx clang --disable-ssl	1m 44s
linux gcc --disable-ssl	2m 17s
linux clang --disable-ssl	2m 13s
linux gcc c99	2m 14s
linux clang c99	2m 18s
linux gcc test	7m 58s
linux clang test asan	13m 4s
linux clang test ubsan	9m 3s
linux gcc test --enable-shared	10m 4s
linux clang test --enable-shared	10m 23s
linux gcc test dpdk	7m 51s
linux clang test dpdk	7m 29s
linux gcc test -ljemalloc	8m 13s
linux clang test -ljemalloc	7m 52s
linux gcc --enable-afxdp	2m 21s
linux clang --enable-afxdp	2m 8s
linux gcc dpdk --enable-shared	3m 29s
linux clang dpdk --enable-shared	3m 2s
linux gcc dpdk-shared	2m 28s
linux clang dpdk-shared	2m 15s
linux gcc dpdk-shared --enable-shared	3m 28s
linux clang dpdk-shared --enable-shared	2m 49s
linux gcc m32 --disable-ssl	2m 22s
	2h 5m 53s

Provide feedback