[fix] ffi/filechooser: return false if no filechooser (#633)
[fix] ffi/filechooser: return false if no filechooser (#633)


koreader/koreader-base,koreader/koreader-base,NiLuJe/koreader-base,Frenzie/koreader-base,koreader/koreader-base,Frenzie/koreader-base,koreader/koreader-base,houqp/koreader-base,Frenzie/koreader-base,houqp/koreader-base,Frenzie/koreader-base,NiLuJe/koreader-base,houqp/koreader-base,NiLuJe/koreader-base,NiLuJe/koreader-base,houqp/koreader-base