fix syntax error in postinst

2020.1/aims-desktop/aims-desktop-2020/debian/changelog

+aims-desktop (2020.9) buster; urgency=medium
+
+  * Fix syntax error
+
+ -- Jan Groenewald <jan@aims.ac.za>  Tue, 25 Dec 2018 16:53:28 +0000
+
 aims-desktop (2020.8) buster; urgency=medium
 
   * Fix detection of /etc/X11/app-defaults/XTerm

2020.1/aims-desktop/aims-desktop-2020/debian/postinst

@@ -6,8 +6,10 @@ update-desktop-database
 update-mime-database /usr/share/mime
 
 # For Su Finance system keybindings
-[ -e /etc/X11/app-defaults/XTerm ] && [ ! -e /etc/X11/app-defaults/XTerm.orig ] && \
-(cp /etc/X11/app-defaults/XTerm /etc/X11/app-defaults/XTerm.orig && cat /etc/X11/app-defaults/XTerm.QVT >> /etc/X11/app-defaults/XTerm)
+if [ -e /etc/X11/app-defaults/XTerm ] && [ ! -e /etc/X11/app-defaults/XTerm.orig ]
+then
+        cp /etc/X11/app-defaults/XTerm /etc/X11/app-defaults/XTerm.orig && cat /etc/X11/app-defaults/XTerm.QVT >> /etc/X11/app-defaults/XTerm
+fi
 
 # We play it very conservative, if this file doessn't exist at all,
 # we write it.