Omit parts of BEP events (like stdout, stderr) when the associated artifact uploader cannot upload a particular file.

RELNOTES: None
PiperOrigin-RevId: 204167372
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/TargetCompleteEvent.java b/src/main/java/com/google/devtools/build/lib/analysis/TargetCompleteEvent.java
index 4ae435e..767eac0 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/TargetCompleteEvent.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/TargetCompleteEvent.java
@@ -274,7 +274,9 @@
     for (Artifact artifact : artifacts) {
       String name = artifactNameFunction.apply(artifact);
       String uri = converters.pathConverter().apply(artifact.getPath());
-      builder.addImportantOutput(File.newBuilder().setName(name).setUri(uri).build());
+      if (uri != null) {
+        builder.addImportantOutput(File.newBuilder().setName(name).setUri(uri).build());
+      }
     }
   }