lavfi/f_sendcmd: clear Command on alloc failure

If the command array failed to allocate, the current parsed
Command has to be cleared, else memory allocated for it
would be leaked.

Fix CID 1638635

libavfilter/f_sendcmd.c

@@ -257,6 +257,7 @@ static int parse_commands(Command **cmds, int *nb_cmds, int interval_count,
             if (!*cmds) {
                 av_log(log_ctx, AV_LOG_ERROR,
                        "Could not (re)allocate command array\n");
+                clear_command(&cmd);
                 return AVERROR(ENOMEM);
             }
         }