fix build on windows

CATSerial.pas

@@ -21,9 +21,10 @@ unit CATSerial;
 interface
 
 uses
-  Classes, SysUtils, SyncObjs,
+  Classes, SysUtils,
   Serial,   // FPC cross-platform serial unit
   {$IFDEF MSWINDOWS}Windows,{$ENDIF}
+  SyncObjs,
   CATEngine;
 
 const
@@ -120,10 +121,10 @@ begin
   {$ENDIF}
 
   case cfg.Parity of
-    cspNone: par := NoneParity;
-    cspOdd:  par := OddParity;
-    cspEven: par := EvenParity;
-  else       par := NoneParity;
+    cspNone: par := Serial.NoneParity;
+    cspOdd:  par := Serial.OddParity;
+    cspEven: par := Serial.EvenParity;
+  else       par := Serial.NoneParity;
   end;
 
   SerSetParams(h, cfg.BaudRate, cfg.DataBits, par, cfg.StopBits, []);
@@ -166,7 +167,11 @@ begin
     end;
   finally
     SerClose(FHandle);
+    {$IFDEF MSWINDOWS}
+    FOwner.Handle := INVALID_HANDLE_VALUE;
+    {$ELSE}
     FOwner.Handle := -1;
+    {$ENDIF}
   end;
 end;
 
@@ -177,7 +182,11 @@ begin
   inherited Create;
   FEngine := AEngine;
   FConfig := ACfg;
+  {$IFDEF MSWINDOWS}
+  FHandle := INVALID_HANDLE_VALUE;
+  {$ELSE}
   FHandle := -1;
+  {$ENDIF}
   FLock   := TCriticalSection.Create;
   FActive := False;
 end;
@@ -211,11 +220,16 @@ end;
 procedure TCATSerialPort.SendStr(const S: string);
 var buf: AnsiString;
 begin
+  {$IFDEF MSWINDOWS}
+  if FHandle = INVALID_HANDLE_VALUE then Exit;
+  {$ELSE}
   if FHandle < 0 then Exit;
+  {$ENDIF}
   FLock.Acquire;
   try
     buf := AnsiString(S);
-    SerWrite(FHandle, buf[1], Length(buf));
+    if Length(buf) > 0 then
+      SerWrite(FHandle, buf[1], Length(buf));
   except
     // ignore write errors (port may have been closed)
   end;