Bug 2071: File panels malfunctions when files are dropped from other application to it

https://winscp.net/tracker/2071
(cherry picked from commit 3af994733bab7b8be3a2c0d23fe8f49c22b47ca3)

Source commit: d9d4081763facfade725fdb28c0f2d77f0ce58af

source/packages/dragndrop/DragDrop.pas

@@ -1416,7 +1416,7 @@ begin
     end;
     if dwEffect <> DROPEFFECT_NONE then
     begin
-      if FOwner.FBTF then SetForegroundWindow((FOwner.Owner as TWinControl).Handle);
+      if FOwner.FBTF then SetForegroundWindow(GetParentForm(FOwner.Owner as TWinControl).Handle);
       TDragDrop(FOwner).FdwEffect := dwEffect;
       TDragDrop(FOwner).FgrfKeyState := KeyState;
       TDragDrop(FOwner).Fpt := pt;