Format 0 second durations correctly

Fixes issue 4165
Unit test for issue 4165

Change-Id: I844da30cdcd5233b07ab8435673b0806fb206448
Reviewed-on: http://gerrit.dmdirc.com/1283
Automatic-Compile: DMDirc Local Commits <dmdirc@googlemail.com>
Reviewed-by: Gregory Holmes <greg@dmdirc.com>

src/com/dmdirc/ui/messages/Formatter.java

@@ -199,7 +199,7 @@ public final class Formatter {
         seconds -= doDuration(buff, seconds, 60, "minute");
         seconds -= doDuration(buff, seconds, 1, "second");
         
-        return buff.toString();
+        return buff.length() == 0 ? "0 seconds" : buff.toString();
     }
     
     /**

test/com/dmdirc/ui/messages/FormatterTest.java

@@ -88,4 +88,10 @@ public class FormatterTest {
         assertEquals("1 day, 10 minutes, 1 second", Formatter.formatDuration(87001));
     }
 
+    @Test
+    public void testFormatNoSeconds() {
+        assertEquals("0 seconds", Formatter.formatDuration(0));
+        assertEquals("0 seconds", Formatter.formatDuration(-100));
+    }
+
 }