[discovery-proxy] remove assert checks on query name parse errors

Remove the `assert` checks on query name parse errors and instead skip
over such entries. Query names are external input (received as DNS
query message from other devices) and discovery proxy code should not
assume that external input will follow the proper query name format.

src/sdp_proxy/discovery_proxy.cpp

@@ -214,11 +214,9 @@ void DiscoveryProxy::OnServiceDiscovered(const std::string
         {
         case OT_DNSSD_QUERY_TYPE_BROWSE:
             splitError = SplitFullServiceName(queryName, serviceName, domain);
-            assert(splitError == OTBR_ERROR_NONE);
             break;
         case OT_DNSSD_QUERY_TYPE_RESOLVE:
             splitError = SplitFullServiceInstanceName(queryName, instanceName, serviceName, domain);
-            assert(splitError == OTBR_ERROR_NONE);
             break;
         default:
             splitError = OTBR_ERROR_NOT_FOUND;
@@ -284,8 +282,13 @@ void DiscoveryProxy::OnHostDiscovered(const std::string
         {
             continue;
         }
+
         splitError = SplitFullHostName(queryName, hostName, domain);
-        assert(splitError == OTBR_ERROR_NONE);
+
+        if (splitError != OTBR_ERROR_NONE)
+        {
+            continue;
+        }
 
         if (DnsLabelsEqual(hostName, aHostName))
         {