Fixed: Don't collapse episode titles when episode titles contain Part x only

src/NzbDrone.Core.Test/OrganizerTests/FileNameBuilderTests/EpisodeTitleCollapseFixture.cs

@@ -97,5 +97,17 @@ namespace NzbDrone.Core.Test.OrganizerTests.FileNameBuilderTests
             Subject.BuildFileName(new List<Episode> { _episode1, _episode2 }, _series, _episodeFile)
                    .Should().Be("South Park - S15E06-E07 - Hello + World");
         }
+
+        [Test]
+        public void should_not_collaspe_when_result_is_empty()
+        {
+            _namingConfig.StandardEpisodeFormat = "{Episode Title}";
+
+            _episode1.Title = "Part 1";
+            _episode2.Title = "Part 2";
+
+            Subject.BuildFileName(new List<Episode> { _episode1, _episode2 }, _series, _episodeFile)
+                   .Should().Be("Part 1 + Part 2");
+        }
     }
 }

src/NzbDrone.Core/Organizer/FileNameBuilder.cs

@@ -684,10 +684,17 @@ namespace NzbDrone.Core.Organizer
                 return episodes.First().Title.TrimEnd(EpisodeTitleTrimCharacters);
             }
 
-            var titles = episodes
-                .Select(c => c.Title.TrimEnd(EpisodeTitleTrimCharacters))
-                .Select(CleanupEpisodeTitle)
-                .Distinct();
+            var titles = episodes.Select(c => c.Title.TrimEnd(EpisodeTitleTrimCharacters))
+                                 .Select(CleanupEpisodeTitle)
+                                 .Distinct()
+                                 .ToList();
+
+            if (titles.All(t => t.IsNullOrWhiteSpace()))
+            {
+                titles = episodes.Select(c => c.Title.TrimEnd(EpisodeTitleTrimCharacters))
+                                 .Distinct()
+                                 .ToList();
+            }
 
             return string.Join(separator, titles);
         }