Do not fail in Loga::Event#to_s when there is no timestamp

lib/loga/event.rb

@@ -11,7 +11,7 @@ def initialize(opts = {})
     end
 
     def to_s
-      output = ["#{timestamp.iso8601(3)} #{message}"]
+      output = [message_with_time]
       if exception
         output.push exception.to_s
         output.push exception.backtrace.join("\n")
@@ -23,6 +23,14 @@ def to_s
 
     private
 
+    def message_with_time
+      if timestamp
+        "#{timestamp.iso8601(3)} #{message}"
+      else
+        message
+      end
+    end
+
     # Guard against Encoding::UndefinedConversionError
     # http://stackoverflow.com/questions/13003287/encodingundefinedconversionerror
     def safe_encode(text)

spec/unit/loga/event_spec.rb

@@ -38,6 +38,14 @@
         expect(subject.to_s).to eql("#{time_anchor.iso8601(3)} Hello World")
       end
     end
+
+    context 'when no timestamp' do
+      let(:opts) { { message: 'Hello World' } }
+
+      it 'will render the message without it' do
+        expect(subject.to_s).to eql('Hello World')
+      end
+    end
   end
 
   describe '#inspect' do