add documentation regarding issue with fcl-web on FPC 3.0.4

Author: zamronypj

known-issues/index.md

@@ -210,6 +210,12 @@ Indy library also cause some warnings to be emitted during compilation. If your
 
 This may cause compilation to stop, so if you use Indy, you may want to make it relax by using `-Se` configuration which stops only on error.
 
+## <a name="empty-response-in-fpc-3.0.4-fcl-web"></a>Fano web application with TFpHttpServer compiled with FPC 3.0.4 returns empty response.
+
+Before version 1.14.1, Fano web application using TFpHttpServer that is compiled with FPC 3.0.4 will return empty response. [This is bug](https://github.com/fanoframework/fano/issues/28) and cause by different behavior of FileExists() between FPC 3.0.4 and FPC 3.2.0.
+
+In FPC 3.0.4 or older, FileExists() in Linux/Unix returns true if input name is existing file or directory. In FPC 3.2.0, FileExists() in Linux/Unix returns false if input name is existing directory.
+
 ## Explore more
 
 - [Getting Started](/getting-started)