Bugfix/series cover not setting (#527)

* Fixed an issue where cover generation was failing on first add due to not checking correctly on First Volume.

API.Tests/Services/MetadataServiceTests.cs

@@ -36,6 +36,13 @@ namespace API.Tests.Services
             }, false, false));
         }
 
+        [Fact]
+        public void ShouldUpdateCoverImage_OnFirstRunSeries()
+        {
+            // Represents first run
+            Assert.True(MetadataService.ShouldUpdateCoverImage(null,null, false, false));
+        }
+
         [Fact]
         public void ShouldUpdateCoverImage_OnSecondRun_FileModified()
         {