Fix assorted ErrorProne warnings.

RELNOTES: None.
PiperOrigin-RevId: 167574104
diff --git a/src/main/java/com/google/devtools/build/lib/packages/RuleClass.java b/src/main/java/com/google/devtools/build/lib/packages/RuleClass.java
index 7cbb25f..3a222db 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/RuleClass.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/RuleClass.java
@@ -1688,7 +1688,7 @@
       if (license == null) {
         license = pkgBuilder.getDefaultLicense();
       }
-      if (license == License.NO_LICENSE) {
+      if (!license.isSpecified()) {
         rule.reportError("third-party rule '" + rule.getLabel() + "' lacks a license declaration "
                          + "with one of the following types: notice, reciprocal, permissive, "
                          + "restricted, unencumbered, by_exception_only",