Handle cases when PGP key metadata is 'nil'

app/models/rails/keyserver/key/pgp.rb

@@ -15,7 +15,7 @@ def self.extension
         Engine.config.key_host = nil
 
         def derive_metadata_if_empty
-          derive_metadata if metadata.empty?
+          derive_metadata if metadata.blank?
         end
 
         # Pick the one without primar key grip.

spec/models/rails/key/pgp_spec.rb

@@ -796,6 +796,23 @@
     end
   end
 
+  describe "#derive_metadata_if_empty" do
+    context "with nil metadata" do
+      let(:key) do
+        FactoryBot.build(:rails_keyserver_key_pgp).tap do |k|
+          allow(k).to receive(:metadata).and_return(nil)
+          allow(k).to receive(:derive_metadata)
+          expect(k.metadata).to be_nil
+        end
+      end
+
+      it "runs #derive_metadata_if_empty" do
+        expect(key).to receive :derive_metadata
+        key.derive_metadata_if_empty
+      end
+    end
+  end
+
   # - wrong key
   #
   # …