Util: more checks in `get_dns_txt_records_base`

src/util.cpp

@@ -508,6 +508,7 @@ bool get_dns_txt_records_base(const std::string& host, Callback<void, const char
 	}
 
 #ifdef _WIN32
+	try {
 		PDNS_RECORD pQueryResults;
 		if (DnsQuery(host.c_str(), DNS_TYPE_TEXT, DNS_QUERY_STANDARD, NULL, &pQueryResults, NULL) != 0) {
 			return false;
@@ -516,14 +517,20 @@ bool get_dns_txt_records_base(const std::string& host, Callback<void, const char
 		for (PDNS_RECORD p = pQueryResults; p; p = p->pNext) {
 			for (size_t j = 0; j < p->Data.TXT.dwStringCount; ++j) {
 				const char* s = p->Data.TXT.pStringArray[j];
+				if (s) {
 					const size_t n = strlen(s);
 					if (n > 0) {
 						callback(s, n);
 					}
 				}
 			}
+		}
 
 		DnsRecordListFree(pQueryResults, DnsFreeRecordList);
+	}
+	catch (...) {
+		return false;
+	}
 
 	return true;
 #elif defined(HAVE_RES_QUERY)