Fix a double-free or use-after-free issue with Guile-SSH used
with Guile 2.2.  See <https://bugs.gnu.org/26976>.

diff --git a/libguile-ssh/channel-type.c b/libguile-ssh/channel-type.c
index 3dd641f..0839854 100644
--- a/libguile-ssh/channel-type.c
+++ b/libguile-ssh/channel-type.c
@@ -229,10 +229,11 @@ ptob_close (SCM channel)
       ssh_channel_free (ch->ssh_channel);
     }
 
+  SCM_SETSTREAM (channel, NULL);
+
 #if USING_GUILE_BEFORE_2_2
   scm_gc_free (pt->write_buf, pt->write_buf_size, "port write buffer");
   scm_gc_free (pt->read_buf,  pt->read_buf_size, "port read buffer");
-  SCM_SETSTREAM (channel, NULL);
 
   return 0;
 #endif
diff --git a/libguile-ssh/sftp-file-type.c b/libguile-ssh/sftp-file-type.c
index 8879924..f87cf03 100644
--- a/libguile-ssh/sftp-file-type.c
+++ b/libguile-ssh/sftp-file-type.c
@@ -224,10 +224,11 @@ ptob_close (SCM sftp_file)
       sftp_close (fd->file);
     }
 
+  SCM_SETSTREAM (sftp_file, NULL);
+
 #if USING_GUILE_BEFORE_2_2
   scm_gc_free (pt->write_buf, pt->write_buf_size, "port write buffer");
   scm_gc_free (pt->read_buf,  pt->read_buf_size, "port read buffer");
-  SCM_SETSTREAM (sftp_file, NULL);
 
   return 1;
 #endif