[infrastructure] move infered nullness warnings to error and update EEA (#8949)

Signed-off-by: Jan N. Klug <jan.n.klug@rub.de>

bundles/org.openhab.binding.luftdateninfo/src/main/java/org/openhab/binding/luftdateninfo/internal/handler/HTTPHandler.java

@@ -14,6 +14,7 @@ package org.openhab.binding.luftdateninfo.internal.handler;
 
 import java.time.LocalDateTime;
 import java.util.List;
+import java.util.Objects;
 import java.util.concurrent.TimeUnit;
 
 import org.eclipse.jdt.annotation.NonNullByDefault;
@@ -82,7 +83,7 @@ public class HTTPHandler {
                         } else {
                             failure = result.getFailure().getMessage();
                         }
-                        callback.onError(failure);
+                        callback.onError(Objects.requireNonNullElse(failure, "Unknown error"));
                     } else {
                         callback.onResponse(getContentAsString());
                     }