Handle errors when no filter can be found to adapt from the decoder format to the display one.

Backport from 174ded88c536ffc9f9eeb8de96e29cf5e9c9a889 in master

src/video_output/display.c

@@ -414,11 +414,7 @@ static void VoutDisplayCreateRender(vout_display_t *vd)
             break;
     }
     if (!filter)
-    {
-        msg_Err(vd, "VoutDisplayCreateRender FAILED");
-        /* TODO */
-        assert(0);
-    }
+        msg_Err(vd, "Failed to adapt decoder format to display");
 }
 
 static void VoutDisplayDestroyRender(vout_display_t *vd)
@@ -993,6 +989,10 @@ picture_t *vout_FilterDisplay(vout_display_t *vd, picture_t *picture)
     vout_display_owner_sys_t *osys = vd->owner.sys;
 
     assert(osys->filters);
+    if (filter_chain_GetLength(osys->filters) <= 0) {
+        picture_Release(picture);
+        return NULL;
+    }
     return filter_chain_VideoFilter(osys->filters, picture);
 }