Make the iOS (and Android?) app work again

Now one can open another document after closing the first one. Turns
out that throwing an exception to return through the call stack to
SocketPoll::poll() is not necessary after all. But doing
document.reset() as before a86508d815 is
essential.

Change-Id: I248df78bd9b0d3f0962df2126ca394cb746542b8
Reviewed-on: https://gerrit.libreoffice.org/c/online/+/90456
Tested-by: Jenkins CollaboraOffice <jenkinscollaboraoffice@gmail.com>
Reviewed-by: Tor Lillqvist <tml@collabora.com>

kit/Kit.cpp

@@ -2159,9 +2159,7 @@ protected:
 #else
             LOG_INF("Setting TerminationFlag due to 'exit' command.");
             SigUtil::setTerminationFlag();
-
-            // Not really a logic error, but hey. This is expected to be caught in SocketPoll::poll().
-            throw std::logic_error("exit");
+            document.reset();
 #endif
         }
         else if (tokens.equals(0, "tile") || tokens.equals(0, "tilecombine") || tokens.equals(0, "canceltiles") ||