Fix missing error check of bufio.Scanner (#29882)

maybe more

modules/markup/csv/csv.go

@@ -6,6 +6,7 @@ package markup
 import (
 	"bufio"
 	"bytes"
+	"fmt"
 	"html"
 	"io"
 	"regexp"
@@ -123,6 +124,10 @@ func (Renderer) fallbackRender(input io.Reader, tmpBlock *bufio.Writer) error {
 			return err
 		}
 	}
+	err = scan.Err()
+	if err != nil {
+		return fmt.Errorf("scan: %w", err)
+	}
 
 	_, err = tmpBlock.WriteString("</pre>")
 	if err != nil {