html macro loses following space on IE after roundtripping

Found while testing CONF-6006

To reproduce:

Enter wiki markup:

The formula for water is H{html}<SUB>2</SUB>{html} and it is 1g/cm{html}<SUP>3</SUP>{html}

This will display (with the sub and sup effects) as:

The formula for water is H2 and it is 1g/cm3

After roundtripping on IE7 it will display as:

The formula for water is H2and it is 1g/cm3

It works correctly on Firefox and Safari.