Skip `missing` error from genhtml

Similar to aosp/3236160, more detail in b/361334044#comment5

Bug:361334044
Bug:397974576
Change-Id: Ibe9eb2d456b47a4c262a19152e43b09f6c3f6ad4
Test: m atest && atest-dev CarLibHostUnitTest --experimental-coverage -d --host
1 file changed