Backport from [17271]. Patch by aurelien: properly test for NULL.

THANKS

@@ -21,6 +21,7 @@ Arkadiusz Lipiec <A.Lipiec at elka.pw.edu.pl> - Polish translation
 Arkadiusz Miskiewicz <misiek at pld.ORG.PL> - autoconf and Makefile patches
 Arnaud Gomes-do-Vale <arnaud at carrosse.frmug.org> - autoconf patches
 Arwed v. Merkatz <v.merkatz at gmx dot net> - Gamma correction for adjust filter
+Aurelien - Patch for modules/stream_output/rtp.c proper test for NULL
 Basil Achermann <vlc at acherma dot com> - Patch to handle esc and space key events from VLCControl (OSX)
 Barak Ori <barakori at gmail dot com> - Bidi fixes
 Benjamin Mironer <bmironer at noos.fr> - Mac OS X fixes

modules/stream_out/rtp.c

@@ -1636,7 +1636,7 @@ static rtsp_client_t *RtspClientGet( sout_stream_t *p_stream, char *psz_session
 {
     int i;
 
-    if( psz_session ) return NULL;
+    if( !psz_session ) return NULL;
 
     for( i = 0; i < p_stream->p_sys->i_rtsp; i++ )
     {