res_pjsip_pubsub: Fix crash on destruction of empty subscription tree.
[asterisk/asterisk.git] / autoconf / ast_c_compile_check.m4
index 0d49ec3..ed15630 100644 (file)
@@ -22,7 +22,7 @@ AC_DEFUN([AST_C_COMPILE_CHECK],
            [   AC_MSG_RESULT(yes)
                PBX_$1=1
                AC_DEFINE([HAVE_$1], 1, [Define if your system has the $1 headers.])
-               AC_DEFINE([HAVE_$1_VERSION], $4, [Define $1 headers version])
+               m4_ifval([$4], [AC_DEFINE([HAVE_$1_VERSION], $4, [Define $1 headers version])])
            ],
            [       AC_MSG_RESULT(no) ] 
        )