8856 TreeProxy Spatial Grid fix

[par456]

Resolves #8856

A bad line of code was adding an empty row in when it saved. Added code to fix those empty lines and fixed the bug that was causing them.

Graphs are also now working again.

[sme016]

Please reopen and fix. I am using the latest upgrade 7481.

I just started to test the Tree Belt Example again, but the TreeProxy does not display either the Temporal or Spatial data, and it has this error message:
System.NullReferenceException: Object reference not set to an instance of an object.
at UserInterface.Views.Sheet.CalculateColumnWidths(IDrawContext cr) in C:\Users\ContainerAdministrator\AppData\Local\Temp\ApsimX\ApsimNG\Views\Sheet\Sheet.cs:line 508
at UserInterface.Views.Sheet.Initialise(IDrawContext cr) in C:\Users\ContainerAdministrator\AppData\Local\Temp\ApsimX\ApsimNG\Views\Sheet\Sheet.cs:line 372
at UserInterface.Views.SheetWidget.Initialise(Context cr) in C:\Users\ContainerAdministrator\AppData\Local\Temp\ApsimX\ApsimNG\Views\Sheet\SheetWidget.cs:line 108
at UserInterface.Views.SheetWidget.OnDrawn(Context cr) in C:\Users\ContainerAdministrator\AppData\Local\Temp\ApsimX\ApsimNG\Views\Sheet\SheetWidget.cs:line 83