Optimize empty nested sets of errors / warnings during Skyframe evaluation.

--
MOS_MIGRATED_REVID=102559969

1 files changed, 1 insertions, 1 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/collect/nestedset/NestedSetVisitor.java b/src/main/java/com/google/devtools/build/lib/collect/nestedset/NestedSetVisitor.java
index ea8b81093f..edf663d45d 100644
--- a/src/main/java/com/google/devtools/build/lib/collect/nestedset/NestedSetVisitor.java
+++ b/src/main/java/com/google/devtools/build/lib/collect/nestedset/NestedSetVisitor.java
@@ -90,7 +90,7 @@ public final class NestedSetVisitor<E> {
     }
 
     private boolean add(NestedSet<E> set) {
-      return seenSets.add(set);
+      return !set.isEmpty() && seenSets.add(set);
     }
   }
 }