Workaround for godot empty array synced bug

[TheDuckCow]

Appears to be working when copied into the wheel steal project. The match lane issue was happening when they were properly de-synced but then zero array length, hence failing on reference [0].

Closes https://github.com/TheDuckCow/godot-road-generator/issues/86

[bdog2112]

What are the steps to re-create the problem that you're addressing? (It may be a different problem than the one I am thinking.)

Using the following testing steps, the arrays are still synced:

• Create a new Scene with RoadNetwork node as root
• Select root node and click "Create>2x2 road" in 3D view
• Save Scene and close it
• Re-open Scene
• Select first RoadPoint, go to Edit RoadPoint panel, and click "+" to add a lane
• Observe that adding a lane to the first RoadPoint also adds a lane to the second RoadPoint. The arrays are synced.

To implement a non-holistic fix simply change the number of lanes from the defaults, save, and re-open. Then, the individual RoadPoints will behave as expected (as long as they don't have the default values).

A holistic fix entails one of two possible solutions:

1. Fix Godot ;-)
2. Insure that RoadGen ALWAYS saves all the elements of RoadPoint arrays to Scene files. (This rule probably also applies to arrays in all other classes, as well.)

[TheDuckCow]

Note to self: move default export vars out of the export var def, and move into init, and verify that default values are saved to the scene files when used.

[bdog2112]

Just wanted to add that this post appears related to the synced array problem and further supports the potential effectiveness of the proposed fix.

[TheDuckCow]

Great work investigating this - I've made the change, found I could not reproduce following your instructions here (a sign the fix worked), and then when reverting the change, I found it immediately occurred just as you described. So I'm pretty confident this is working with this update!