Fix another issue with fallbacks

include/mtx/events/common.hpp

include/mtx/events_impl.hpp

lib/structs/events/common.cpp

lib/structs/events/encrypted.cpp

lib/structs/events/messages/audio.cpp

lib/structs/events/messages/emote.cpp

lib/structs/events/messages/file.cpp

lib/structs/events/messages/image.cpp

lib/structs/events/messages/notice.cpp

lib/structs/events/messages/text.cpp

lib/structs/events/messages/video.cpp

lib/structs/events/reaction.cpp