applayer: allow rust parsers to have only one probe

src/app-layer-register.c

@@ -54,7 +54,7 @@ AppProto AppLayerRegisterProtocolDetection(const struct AppLayerParser *p, int e
 
     AppLayerProtoDetectRegisterProtocol(alproto, p->name);
 
-    if (p->ProbeTS == NULL || p->ProbeTC == NULL) {
+    if (p->ProbeTS == NULL && p->ProbeTC == NULL) {
         return alproto;
     }