Added Path validator for SeriesModule

NzbDrone.Api/Series/SeriesModule.cs

@@ -29,6 +29,7 @@ namespace NzbDrone.Api.Series
 
             Get["/{slug}"] = o => GetSeries((string)o.slug.ToString());
 
+            SharedValidator.RuleFor(s => s.Path).NotEmpty();
             SharedValidator.RuleFor(s => s.QualityProfileId).ValidId();
 
             PostValidator.RuleFor(s => s.Title).NotEmpty();