media player and media: add sanity checks

Sources/VLCMedia.m

@@ -218,16 +218,17 @@ static void HandleMediaParsedChanged(const libvlc_event_t * event, void * self)
 - (void)dealloc
 {
     libvlc_event_manager_t * p_em = libvlc_media_event_manager(p_md);
-    libvlc_event_detach(p_em, libvlc_MediaMetaChanged,     HandleMediaMetaChanged,     (__bridge void *)(self));
-    libvlc_event_detach(p_em, libvlc_MediaDurationChanged, HandleMediaDurationChanged, (__bridge void *)(self));
-    libvlc_event_detach(p_em, libvlc_MediaStateChanged,    HandleMediaStateChanged,    (__bridge void *)(self));
-    libvlc_event_detach(p_em, libvlc_MediaSubItemAdded,    HandleMediaSubItemAdded,    (__bridge void *)(self));
-    libvlc_event_detach(p_em, libvlc_MediaParsedChanged,   HandleMediaParsedChanged,   (__bridge void *)(self));
+    if (p_em) {
+        libvlc_event_detach(p_em, libvlc_MediaMetaChanged,     HandleMediaMetaChanged,     (__bridge void *)(self));
+        libvlc_event_detach(p_em, libvlc_MediaDurationChanged, HandleMediaDurationChanged, (__bridge void *)(self));
+        libvlc_event_detach(p_em, libvlc_MediaStateChanged,    HandleMediaStateChanged,    (__bridge void *)(self));
+        libvlc_event_detach(p_em, libvlc_MediaSubItemAdded,    HandleMediaSubItemAdded,    (__bridge void *)(self));
+        libvlc_event_detach(p_em, libvlc_MediaParsedChanged,   HandleMediaParsedChanged,   (__bridge void *)(self));
+    }
 
     [[VLCEventManager sharedManager] cancelCallToObject:self];
 
     libvlc_media_release( p_md );
-
 }
 
 - (NSString *)description
@@ -749,11 +750,13 @@ NSString *const VLCMediaTracksInformationTextEncoding = @"encoding"; // NSString
     libvlc_media_set_user_data(p_md, (__bridge void*)self);
 
     libvlc_event_manager_t * p_em = libvlc_media_event_manager( p_md );
-    libvlc_event_attach(p_em, libvlc_MediaMetaChanged,     HandleMediaMetaChanged,     (__bridge void *)(self));
-    libvlc_event_attach(p_em, libvlc_MediaDurationChanged, HandleMediaDurationChanged, (__bridge void *)(self));
-    libvlc_event_attach(p_em, libvlc_MediaStateChanged,    HandleMediaStateChanged,    (__bridge void *)(self));
-    libvlc_event_attach(p_em, libvlc_MediaSubItemAdded,    HandleMediaSubItemAdded,    (__bridge void *)(self));
-    libvlc_event_attach(p_em, libvlc_MediaParsedChanged,   HandleMediaParsedChanged,   (__bridge void *)(self));
+    if (p_em) {
+        libvlc_event_attach(p_em, libvlc_MediaMetaChanged,     HandleMediaMetaChanged,     (__bridge void *)(self));
+        libvlc_event_attach(p_em, libvlc_MediaDurationChanged, HandleMediaDurationChanged, (__bridge void *)(self));
+        libvlc_event_attach(p_em, libvlc_MediaStateChanged,    HandleMediaStateChanged,    (__bridge void *)(self));
+        libvlc_event_attach(p_em, libvlc_MediaSubItemAdded,    HandleMediaSubItemAdded,    (__bridge void *)(self));
+        libvlc_event_attach(p_em, libvlc_MediaParsedChanged,   HandleMediaParsedChanged,   (__bridge void *)(self));
+    }
 
     libvlc_media_list_t * p_mlist = libvlc_media_subitems( p_md );
 

Sources/VLCMediaPlayer.m

@@ -1218,6 +1218,9 @@ static void HandleMediaPlayerMediaChanged(const libvlc_event_t * event, void * s
 {
     // Attach event observers into the media instance
     libvlc_event_manager_t * p_em = libvlc_media_player_event_manager(_playerInstance);
+    if (!p_em)
+        return;
+
     libvlc_event_attach(p_em, libvlc_MediaPlayerPlaying,          HandleMediaInstanceStateChanged, (__bridge void *)(self));
     libvlc_event_attach(p_em, libvlc_MediaPlayerPaused,           HandleMediaInstanceStateChanged, (__bridge void *)(self));
     libvlc_event_attach(p_em, libvlc_MediaPlayerEncounteredError, HandleMediaInstanceStateChanged, (__bridge void *)(self));
@@ -1234,6 +1237,9 @@ static void HandleMediaPlayerMediaChanged(const libvlc_event_t * event, void * s
 - (void)unregisterObservers
 {
     libvlc_event_manager_t * p_em = libvlc_media_player_event_manager(_playerInstance);
+    if (!p_em)
+        return;
+
     libvlc_event_detach(p_em, libvlc_MediaPlayerPlaying,          HandleMediaInstanceStateChanged, (__bridge void *)(self));
     libvlc_event_detach(p_em, libvlc_MediaPlayerPaused,           HandleMediaInstanceStateChanged, (__bridge void *)(self));
     libvlc_event_detach(p_em, libvlc_MediaPlayerEncounteredError, HandleMediaInstanceStateChanged, (__bridge void *)(self));