HTML output shows only the first difference

Found in Diffoscope 259 on Debian testing.

The HTML-Output (both --html and --html-dir) shows only the first difference in a file, while the text output shows all differences.

To reproduce:

rm myfile1
for i in `seq 1 50`; do echo "Line ${i}" >> myfile1; done
cp myfile1 myfile2
sed -i -e 's/Line 4$/Line 4b/;s/Line 35/Line 35b/' myfile2
diffoscope myfile1 myfile2 --html my.html # Only the first difference is shown
diffoscope myfile1 myfile2 # Correct output