(Hopefully) Stops cryopodded contract targets from breaking contractor uplinks (#59742)

This PR aims to stop contractor uplinks from breaking due to having a target cryopod. When a contract target enters cryosleep, it now manually rerolls the contract.

This PR is admittedly somewhat bandaid-y, as contractors are slotted for removal soon, apparently.

code/modules/modular_computers/file_system/programs/antagonist/contract_uplink.dm

@@ -165,6 +165,11 @@
 			))
 
 		for (var/datum/syndicate_contract/contract in traitor_data.contractor_hub.assigned_contracts)
+			if(!contract.contract)
+				stack_trace("Syndiate contract with null contract objective found in [traitor_data.owner]'s contractor hub!")
+				contract.status = CONTRACT_STATUS_ABORTED
+				continue
+
 			data["contracts"] += list(list(
 				"target" = contract.contract.target,
 				"target_rank" = contract.target_rank,