Fix minor nit in debian/rules file

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/debian/rules b/debian/rules
index e36d559..1296cb9 100755
--- a/debian/rules
+++ b/debian/rules
@@ -321,7 +321,7 @@
 	ln -s et/com_err.h ${tmpdir}/usr/include
 
 	dh_movefiles
-	test -z `find ${tmpdir} -type f`
+	test -z "`find ${tmpdir} -type f`"
 
   # specially-built MIPS libs
 ifneq ($(ismips),)