Missed a common case for needing to extend the buffer.

(closes issue #14716)
 Reported by: sum
 Patches: 
       20090402__bug14716.diff.txt uploaded by tilghman (license 14)
 Tested by: sum


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@186021 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/strings.c

@@ -143,7 +143,8 @@ char *__ast_str_helper2(struct ast_str **buf, size_t maxlen, const char *src, si
 		maxlen--;
 		(*buf)->__AST_STR_USED++;
 
-		if (dynamic && (!maxlen || (escapecommas && !(maxlen - 1)))) {
+		if ((ptr >= (*buf)->__AST_STR_STR + (*buf)->__AST_STR_LEN - 3) ||
+			(dynamic && (!maxlen || (escapecommas && !(maxlen - 1))))) {
 			char *oldbase = (*buf)->__AST_STR_STR;
 			size_t old = (*buf)->__AST_STR_LEN;
 			if (ast_str_make_space(buf, (*buf)->__AST_STR_LEN * 2)) {