Fix duplicate coop save file creation.

Author: GoogleFrog

LuaMenu/widgets/api_campaign_data.lua

@@ -482,11 +482,16 @@ local function LoadGame(saveData, refreshGUI)
 	end
 end
 
-local function StartNewGame()
+local function StartNewGame(overrideCampaignID)
 	WG.Chobby.Configuration:SetConfigValue("campaignSaveFile", nil) -- Save name generated by campaign data handler
 	local campaignConfig = WG.Chobby.Configuration.campaignConfig
 	ResetGamedata()
-	GenerateCampaignID()
+	
+	if overrideCampaignID then
+		gamedata.campaignID = overrideCampaignID
+	else
+		GenerateCampaignID()
+	end
 
 	local planets = campaignConfig.planetDefs.initialPlanets
 	UnlockRewardSet(campaignConfig.initialUnlocks)
@@ -586,7 +591,7 @@ function externalFunctions.ApplyCampaignPartialSaveData(saveData)
 		if existingSave then
 			LoadGameByFilename(existingSave)
 		else
-			StartNewGame()
+			StartNewGame(saveData.campaignID)
 			SetupNewSave(commander.name, saveData.difficultySetting, saveData.campaignID)
 		end
 	end