Fix customdsdata property always returning null.

src/Directory.Build.props

@@ -2,7 +2,7 @@
   <PropertyGroup>
     <!--change these in each release-->
     <VersionPrefix>4.0.0.0</VersionPrefix>
-    <VersionSuffix>alpha.11</VersionSuffix>
+    <VersionSuffix>alpha.12</VersionSuffix>
     
     <!--keep it the same until major # changes-->
     <AssemblyVersion>4.0.0.0</AssemblyVersion>

src/NTwain/TwainAppSession.PropEvents.cs

@@ -86,6 +86,7 @@ partial class TwainAppSession
                         var lockedPtr = Lock(data.hData);
                         var bytes = new byte[data.InfoLength];
                         Marshal.Copy(lockedPtr, bytes, 0, bytes.Length);
+                        return bytes;
                     }
                     finally
                     {
@@ -93,7 +94,6 @@ partial class TwainAppSession
                         Free(data.hData);
                     }
                 }
-                //return Array.Empty<byte>();
             }
             return null;
         }