Fix freeaddrinfo(NULL).

Bug: https://code.google.com/p/android/issues/detail?id=13228
Change-Id: I5e3b126d90d750a93ac0b8872198e50ba047e603
diff --git a/libc/dns/net/getaddrinfo.c b/libc/dns/net/getaddrinfo.c
index f0d522a..c73c085 100644
--- a/libc/dns/net/getaddrinfo.c
+++ b/libc/dns/net/getaddrinfo.c
@@ -324,7 +324,11 @@
 {
 	struct addrinfo *next;
 
-	assert(ai != NULL);
+#if __ANDROID__
+	if (ai == NULL) return;
+#else
+	_DIAGASSERT(ai != NULL);
+#endif
 
 	do {
 		next = ai->ai_next;