Allow enabling of Hold Map Center even when GPS is disabled

At present the Hold Map Center button (bottom left corner) will be enabled (blue)

1. if restored from previous enabled state at exit (even if GPS position is disabled)
2. or if GPS is enabled (but position invalid/ unknown) the user can enable the Hold Map Center button then subsequently disable the GPS again
   
3. or if GPS position is enabled and the button is tapped

If the GPS position is disabled the user can disable the Hold Map Center function but not subsequently re-enable it. This is inconsistent with behavior of list items #1 and #2 and inconvenient. For example if a Preset is selected that has Hold Map Center enabled but the GPS is disabled then the function is disabled. I would suggest the Hold Map Center button can be enabled (blue) anytime, instead of silently ignored, and subsequently when the GPS position is known the map position is simply moved accordingly.