Better validation for Imdb Ids from lists

Fixes #5674

src/NzbDrone.Core.Test/ParserTests/ParserFixture.cs

@@ -162,6 +162,7 @@ public void should_parse_imdb_in_title(string postTitle, string imdb)
             parsed.ImdbId.Should().Be(imdb);
         }
 
+        [TestCase("asfd", null)]
         [TestCase("123", "tt0000123")]
         [TestCase("1234567", "tt1234567")]
         [TestCase("tt1234567", "tt1234567")]

src/NzbDrone.Core/MetadataSource/SkyHook/SkyHookProxy.cs

@@ -125,6 +125,13 @@ public List<Movie> GetBulkMovieInfo(List<int> tmdbIds)
 
         public Movie GetMovieByImdbId(string imdbId)
         {
+            imdbId = Parser.Parser.NormalizeImdbId(imdbId);
+
+            if (imdbId == null)
+            {
+                return null;
+            }
+
             var httpRequest = _radarrMetadata.Create()
                                              .SetSegment("route", "movie/imdb")
                                              .Resource(imdbId.ToString())

src/NzbDrone.Core/Parser/Parser.cs

@@ -357,6 +357,13 @@ public static string ReplaceGermanUmlauts(string s)
 
         public static string NormalizeImdbId(string imdbId)
         {
+            var imdbRegex = new Regex(@"^(\d{1,10}|(tt)\d{1,10})$");
+
+            if (!imdbRegex.IsMatch(imdbId))
+            {
+                return null;
+            }
+
             if (imdbId.Length > 2)
             {
                 imdbId = imdbId.Replace("tt", "").PadLeft(7, '0');