Fix npe (#582)

src/main/kotlin/io/emeraldpay/dshackle/upstream/generic/GenericUpstream.kt

@@ -246,19 +246,20 @@ open class GenericUpstream(
     }
 
     private fun detectSettings() {
+        if (settingsDetector != null) {
             settingsDetectorSubscription.set(
                 Flux.interval(
                     Duration.ZERO,
                     Duration.ofSeconds(getOptions().validationInterval.toLong() * 5),
                 ).flatMap {
                     Flux.merge(
-                    settingsDetector?.detectLabels()
+                        settingsDetector.detectLabels()
-                        ?.doOnNext { label ->
+                            .doOnNext { label ->
                                 updateLabels(label)
                                 sendUpstreamStateEvent(UPDATED)
                             },
-                    settingsDetector?.detectClientVersion()
+                        settingsDetector.detectClientVersion()
-                        ?.doOnNext {
+                            .doOnNext {
                                 log.info("Detected node version $it for upstream ${getId()}")
                                 clientVersion.set(it)
                             },
@@ -267,6 +268,7 @@ open class GenericUpstream(
                 }.subscribe(),
             )
         }
+    }
 
     private fun detectRpcMethods(
         config: UpstreamsConfig.Upstream<*>,