Makefile: Use $(NULL) in one more place

diff --git a/src/Makefile.am b/src/Makefile.am
index abffd8902c81700e5e12cbd3004c37da10a391ea..a73eaaedfe9d1199732709ed138c53b437fe081a 100644 (file)
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -101,7 +101,8 @@ shell_public_headers_h =            \
        shell-tray-manager.h            \
        shell-util.h                    \
        shell-window-tracker.h          \
-       shell-wm.h
+       shell-wm.h                      \
+       $(NULL)
 
 if HAVE_NETWORKMANAGER
 shell_public_headers_h +=  shell-network-agent.h