Merge pull request #179 from adamhathcock/tar_fix

Allow empty tar header to be read to know there are no more tar heade…

src/SharpCompress/Common/Tar/Headers/TarHeader.cs

@@ -164,9 +164,9 @@ namespace SharpCompress.Common.Tar.Headers
         {
             byte[] buffer = reader.ReadBytes(BlockSize);
 
-            if (buffer.Length < BlockSize)
+            if (buffer.Length != 0 && buffer.Length < BlockSize)
             {
-                throw new InvalidOperationException();
+                throw new InvalidOperationException("Buffer is invalid size");
             }
             return buffer;
         }