ffools/ffmpeg_filter: stop trying to handle an unreachable state

ifilter_send_eof() will fail if the input has no real or fallback
parameters, so there is no need to handle the case of some inputs being
in EOF state yet having no parameters.

fftools/ffmpeg.c

@@ -944,7 +944,7 @@ static int choose_output(OutputStream **post)
                    INT64_MIN : ost->last_mux_dts;
         }
 
-        if (!ost->initialized && !ost->inputs_done && !ost->finished) {
+        if (!ost->initialized && !ost->finished) {
             ost_min = ost;
             break;
         }