xcap_client: handle return code for strchr()

(cherry picked from commit 8147009)

src/modules/xcap_client/xcap_client.c

@@ -310,24 +310,33 @@ int parse_doc_url(str doc_url, char** serv_addr, xcap_doc_sel_t* doc_sel)
 	char* sl, *str_type;
 
 	sl= strchr(doc_url.s, '/');
+	if(sl==NULL) {
+		return -1;
+	}
 	*sl= '\0';
 	*serv_addr= doc_url.s;
 
 	sl++;
 	doc_sel->auid.s= sl;
 	sl= strchr(sl, '/');
+	if(sl==NULL) {
+		return -1;
+	}
 	doc_sel->auid.len= sl- doc_sel->auid.s;
 
 	sl++;
 	str_type= sl;
 	sl= strchr(sl, '/');
+	if(sl==NULL) {
+		return -1;
+	}
 	*sl= '\0';
 
-	if(strcasecmp(str_type, "users")== 0)
+	if(strcasecmp(str_type, "users")== 0) {
 		doc_sel->type= USERS_TYPE;
-	else
-	if(strcasecmp(str_type, "group")== 0)
+	} else if(strcasecmp(str_type, "group")== 0) {
 		doc_sel->type= GLOBAL_TYPE;
+	}
 
 	sl++;