Add @Nullable annotations where they were missing.

PiperOrigin-RevId: 459211611
Change-Id: I9b281b82c8b3356b3ec735752d9da93239d90105
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/RecursivePackageProviderBackedTargetPatternResolver.java b/src/main/java/com/google/devtools/build/lib/skyframe/RecursivePackageProviderBackedTargetPatternResolver.java
index 1d14e1a..9693f5e 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/RecursivePackageProviderBackedTargetPatternResolver.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/RecursivePackageProviderBackedTargetPatternResolver.java
@@ -60,6 +60,7 @@
 import java.util.concurrent.Callable;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Future;
+import javax.annotation.Nullable;
 
 /** A {@link TargetPatternResolver} backed by a {@link RecursivePackageProvider}. */
 @ThreadCompatible
@@ -108,6 +109,7 @@
   }
 
   @Override
+  @Nullable
   public Target getTargetOrNull(Label label)
       throws InterruptedException, InconsistentFilesystemException {
     try {