fix details and details spec

lib/audit/details.rb

@@ -32,7 +32,14 @@ module Audit
       when :failed_login
         "Failed to login with #{Gitlab::OAuth::Provider.label_for(value).upcase} authentication"
       else
-        "Changed #{value} from #{@details[:from]} to #{@details[:to]}"
+        text_for_change(value)
+      end
+    end
+
+    def text_for_change(value)
+      "Changed #{value}".tap do |changed_string|
+        changed_string << " from #{@details[:from]}" if @details[:from]
+        changed_string << " to #{@details[:to]}" if @details[:to]
       end
     end
   end

spec/lib/audit/details_spec.rb

@@ -75,5 +75,23 @@ describe Audit::Details do
         expect(described_class.humanize(removal_action)).to eq('Removed deploy key')
       end
     end
+
+    context 'change email' do
+      let(:action) do
+        {
+            change: 'email',
+            from: 'a@b.com',
+            to: 'c@b.com',
+            author_name: 'author',
+            target_id: '',
+            target_type: 'Email',
+            target_details: 'Email'
+        }
+      end
+
+      it 'humanizes the removal action' do
+        expect(described_class.humanize(action)).to eq('Removed deploy key')
+      end
+    end
   end
 end