[base64] fix another crash due to broken force_assert conditions

From: Stefan Bühler <stbuehler@web.de>

git-svn-id: svn://svn.lighttpd.net/lighttpd/branches/lighttpd-1.4.x@3119 152afb58-edef-0310-8abb-c4023f1b3aa9

src/base64.c

@@ -142,8 +142,8 @@ size_t li_to_base64_no_padding(char* out, size_t out_length, const unsigned char
 	}
 
 	/* check overflows */
-	force_assert(full_tuples < 2*full_tuples);
-	force_assert(full_tuples < 4*full_tuples);
+	force_assert(full_tuples <= 2*full_tuples);
+	force_assert(full_tuples <= 4*full_tuples);
 	force_assert(4*full_tuples <= 4*full_tuples + out_tuple_remainder);
 	force_assert(require_space <= out_length);