Partymodes: Fix "Select random" button selecting invalid profiles

which would happen if the number of visible profiles matched the number of used profiles or if there were more slots than usable profiles

VocaluxeLib/Menu/CMenuPartyNameSelection.cs

@@ -774,7 +774,8 @@ namespace VocaluxeLib.Menu
                 for (int p = 0; p < _NumPlayerTeams[t]; p++)
                 {
                     int profileID = _NameSelections[_NameSelection].GetRandomUnusedProfile();
-                    _AddPlayer(t, profileID);
+                    if(profileID >= 0) //only add valid profiles
+                        _AddPlayer(t, profileID);
                 }
             }
         }