World: Initialise 'topo_graph' pointer
World: Initialise 'topo_graph' pointer

Previously this member was uninitialised which meant if it was never
used (i.e. parse-only) then the destructor would call delete on a
garbage pointer. Ensure this field is now initialised and switch all
other members that can use class member initialisation instead.

Change-Id: I11f7bb1919e1367eda9ed59b38ef604dbb61e9df
Reviewed-by: Scott Parlane <85029adc3fa41ef14594a57826619713bfe95f25@alliedtelesis.co.nz>
Reviewed-by: Ridge Kennedy <c60c433c4c1ae237d133641099200771ff6f6f30@alliedtelesis.co.nz>
Signed-off-by: Matt Bennett <e3d8681cec70d3da741935b3385821001b249adc@alliedtelesis.co.nz>

ATL-NZ/buildsyspp,alliedtelesis/buildsyspp