Fix some comment typos and errors

1. added missing null guard in 3-Extract-Output-ComplexTypes.usql
2. fixed wrong column name reference in
3-Extract-Output-ComplexTypes.usql
3. added no option output to 4-Output-Options.usql for comparison
4. Fixed comment typos in 6-Extract-withHeaders.usql

Examples/Builtin-UDOs/Builtin-UDOs/3-Extract-Output-ComplexTypes.usql

@@ -34,7 +34,8 @@ FROM @Drivers;
 // Serialize SQL.MAP into string (or byte[]) for serialization
 @OutDrivers = 
  SELECT driver_id, name, street, city, region, zipcode, country
-     , String.Join(",", phone_numbers.Select(p => String.Format("{0}:{1}", p.Key, p.Value))) AS phone_numbers
+      , phone_numbers == null ? null :
+             String.Join(",", phone_numbers.Select(p => String.Format("{0}:{1}", p.Key, p.Value))) AS phone_numbers
 FROM @Drivers;
 
 OUTPUT @OutDrivers TO "/output/builtinUDO/Drivers.csv" USING Outputters.Csv();
@@ -60,7 +61,7 @@ FROM @Trips;
 // Serialize SQL.ARRAY into string (or byte[]) for serialization
 @OutTrips =   
 SELECT date, driver_id, vehicle_id
-     , String.Join(",", trips) AS trips
+     , String.Join(",", trip_ids) AS trips
 FROM @Trips;
 
 

Examples/Builtin-UDOs/Builtin-UDOs/4-Output-Options.usql

@@ -10,6 +10,10 @@ FROM (VALUES
    ,  ("This row contains CR LF \r\n", (double?) 2342, DateTime.Parse("2016-04-05T12:12:12.918"))
    )  AS T(s_col, d_col, dt_col);
 
+OUTPUT @SampleRows
+TO "/output/builtinUDO/nooptions.csv"
+USING Outputters.Csv();
+
 OUTPUT @SampleRows
 TO "/output/builtinUDO/QuotedOptions.csv" 
 USING Outputters.Text(delimiter:'&', quoting: true, escapeCharacter: '$', nullEscape: "\\N");

Examples/Builtin-UDOs/Builtin-UDOs/6-Extract-withHeaders.usql

@@ -69,7 +69,7 @@ USING Outputters.Csv();
 
 ///
 
-// silent:true will skip incorrect number of rows or replaces invalid invalid casts to nullable types. It will not skip encoding errors, allow invalid casts to not-nullable types, or skip a row where a cast error occurs.
+// silent:true will skip incorrect number of columns or replaces invalid casts to nullable types. It will not skip encoding errors, allow invalid casts to not-nullable types, or skip a row where a cast error occurs.
 @silent_r =
     EXTRACT id long?,
             name string,