Fix segfault when rpmbuild stumbles over an empty file list.
The "+ 1" is a remedy for xmalloc(0), which would return NULL.

Index: ./build/files.c
===================================================================
--- ./build/files.c
+++ ./build/files.c
@@ -1380,7 +1380,7 @@ static void genCpioListAndHeader(/*@part
 	: (int *)(fi->bnl + fi->fc);
 /*@=dependenttrans@*/
 
-    fi->apath = xmalloc(fi->fc * sizeof(*fi->apath) + apathlen);
+    fi->apath = xmalloc(fi->fc * sizeof(*fi->apath) + apathlen + 1);
     a = (char *)(fi->apath + fi->fc);
     *a = '\0';