GAG Builder: Aglycon not available after monosaccharide 1 for hyaluronan and keratin / keratan sulfate

**Tool:**
GAG Builder

**Bug Description:**
For the gycosaminoglycan classes hyaluronan and keratin / keratan sulfate, the addition of an aglycon is only available for monosaccharide 2. It cannot be selected for monosaccharide 1.

**To Reproduce:**
Go to glycam.org/gag and click on either Hyaluronan or Keratin / Keratan sulfate. Start building a gag. Note that adding a terminal aglycon is not available after selecting a monosaccharide from set 1.

**Expected behavior**
It should be possible to add the aglycon for either monosaccharide set in all gag families.

**Screenshots**
In the screenshot, the instructions say that it should be possible to add an aglycon, but it is not.