Fix type on return value in HTTPLiveStream::StopStream()

HTTPLiveStream::StopStream() should return a NULL pointer, not
false in an error condition.  This one must have slipped by
earlier.

Fixes #10477 using patch by Gary Buhrmaster.

mythtv/libs/libmythtv/httplivestream.cpp

@@ -882,7 +882,7 @@ DTC::LiveStreamInfo *HTTPLiveStream::StopStream(int id)
         LOG(VB_GENERAL, LOG_ERR, SLOC +
             QString("Unable to remove mark stream stopped for stream %1.")
                     .arg(id));
-        return false;
+        return NULL;
     }
 
     HTTPLiveStream *hls = new HTTPLiveStream(id);