BUILD: Continue to fix some clang's warnings

inc/lektor/common.h

inc/lektor/queue.h

src/base/cmd.c

src/base/commands.c

src/base/common.c

src/base/config.c

src/base/json.c

src/base/launch.c

src/base/segv.c

src/base/uri.c

src/database/cache.c

src/database/find.c

src/main/luka.c

src/mkv/mkv.c

src/mkv/utils.c

src/mkv/write.c

src/module/module_repo.c

src/module/mpv.c

src/net/command.c

src/net/listen.c