opengl: release current context before destroying it

modules/video_output/gl.c

@@ -158,7 +158,10 @@ static int Open (vlc_object_t *obj)
     const vlc_fourcc_t *spu_chromas;
     sys->vgl = vout_display_opengl_New (&vd->fmt, &spu_chromas, sys->gl);
     if (!sys->vgl)
+    {
+        vlc_gl_ReleaseCurrent (sys->gl);
         goto error;
+    }
 
     vd->sys = sys;
     vd->info.has_pictures_invalid = false;
@@ -189,6 +192,8 @@ static void Close (vlc_object_t *obj)
     vout_display_sys_t *sys = vd->sys;
 
     vout_display_opengl_Delete (sys->vgl);
+    vlc_gl_ReleaseCurrent (sys->gl);
+
     vlc_gl_Destroy (sys->gl);
     vout_display_DeleteWindow (vd, sys->window);
     free (sys);