Minor fixes.

Author: And1sS

extra/modules/pb-rule-engine/src/main/java/org/prebid/server/hooks/modules/rule/engine/core/config/RuleParser.java

@@ -5,7 +5,7 @@
 import com.github.benmanes.caffeine.cache.Caffeine;
 import io.vertx.core.Future;
 import io.vertx.core.Vertx;
-import org.prebid.server.exception.PreBidException;
+import org.apache.commons.lang3.ObjectUtils;
 import org.prebid.server.execution.retry.RetryPolicy;
 import org.prebid.server.execution.retry.Retryable;
 import org.prebid.server.hooks.modules.rule.engine.core.rules.PerStageRule;
@@ -67,9 +67,7 @@ public Future<PerStageRule> parseForAccount(String accountId, ObjectNode config)
         }
 
         parseConfig(accountId, config);
-        return cachedRule == null
-                ? Future.failedFuture(new PreBidException("Rule for account " + accountId + " is not ready"))
-                : Future.succeededFuture(cachedRule);
+        return Future.succeededFuture(ObjectUtils.defaultIfNull(cachedRule, PerStageRule.noOp()));
     }
 
     private Instant getConfigTimestamp(ObjectNode config) {

extra/modules/pb-rule-engine/src/main/java/org/prebid/server/hooks/modules/rule/engine/core/rules/PerStageRule.java

@@ -13,8 +13,16 @@
 @Value(staticConstructor = "of")
 public class PerStageRule {
 
+    private static final PerStageRule NO_OP = PerStageRule.builder()
+            .processedAuctionRequestRule(NoOpRule.create())
+            .build();
+
     Instant timestamp;
 
     Rule<BidRequest, RequestRuleContext> processedAuctionRequestRule;
+
+    public static PerStageRule noOp() {
+        return NO_OP;
+    }
 }
 

extra/modules/pb-rule-engine/src/main/java/org/prebid/server/hooks/modules/rule/engine/v1/PbRuleEngineProcessedAuctionRequestHook.java

@@ -92,7 +92,10 @@ private static List<Rejection> toRejections(SeatNonBid seatNonBid) {
 
     private static Map<String, List<Rejection>> toRejections(List<SeatNonBid> seatNonBids) {
         return seatNonBids.stream()
-                .collect(Collectors.toMap(SeatNonBid::getSeat, PbRuleEngineProcessedAuctionRequestHook::toRejections));
+                .collect(Collectors.groupingBy(SeatNonBid::getSeat,
+                        Collectors.flatMapping(
+                                seatNonBid -> toRejections(seatNonBid).stream(),
+                                Collectors.toList())));
     }
 
     private static Future<InvocationResult<AuctionRequestPayload>> failure(Throwable error) {