patch 7.4.1319
Problem:    Tests fail on MS-Windows and on Unix with GUI.
Solution:   Fix unregistering.
diff --git a/src/os_unix.c b/src/os_unix.c
index 65a4b92..ec7d6c1 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -5043,7 +5043,7 @@
     int		fd_in[2];	/* for stdin */
     int		fd_out[2];	/* for stdout */
     int		fd_err[2];	/* for stderr */
-    channel_T	*channel;
+    channel_T	*channel = NULL;
 
     /* default is to fail */
     job->jv_status = JOB_FAILED;