Fixes #20217: Fix '0 VLANs available' in the VLANs table in VLAN Groups (#20261)

* Fixes #20217: hide 0 VLANs available message in VLAN groups

* Simplified fix to improve readability

netbox/ipam/utils.py

@@ -164,7 +164,7 @@ def available_vlans_from_range(vlans, vlan_group, vid_range):
         prev_vid = vlan.vid
 
     # Annotate any remaining available VLANs
-    if prev_vid < max_vid:
+    if prev_vid < max_vid - 1:
         new_vlans.append({
             'vid': prev_vid + 1,
             'vlan_group': vlan_group,