fixed a bug writing fact chunk for WaveFormats with bits per sample set to 0

NAudio/Wave/WaveOutputs/WaveFileWriter.cs

@@ -79,7 +79,7 @@ namespace NAudio.Wave
 
         private void CreateFactChunk()
         {
-            if (this.format.Encoding != WaveFormatEncoding.Pcm)
+            if (HasFactChunk())
             {
                 this.writer.Write(System.Text.Encoding.ASCII.GetBytes("fact"));
                 this.writer.Write((int)4);
@@ -88,6 +88,11 @@ namespace NAudio.Wave
             }
         }
 
+        private bool HasFactChunk()
+        {
+            return this.format.Encoding != WaveFormatEncoding.Pcm && this.format.BitsPerSample != 0;
+        }
+
         /// <summary>
         /// The wave file name or null if not applicable
         /// </summary>
@@ -375,7 +380,7 @@ namespace NAudio.Wave
 
         private void UpdateFactChunk(BinaryWriter writer)
         {
-            if (format.Encoding != WaveFormatEncoding.Pcm)
+            if (HasFactChunk())
             {
                 int bitsPerSample = (format.BitsPerSample * format.Channels);
                 if (bitsPerSample != 0)