fix: guard against null billing plan cache entries

Author: TorstenDittmann

src/lib/stores/billing.ts

@@ -143,7 +143,7 @@ export function getBasePlanFromGroup(billingPlanGroup: BillingPlanGroup): Models
     const plansInfoStore = getPlansInfoStore();
 
     const proPlans = Array.from(plansInfoStore.values()).filter(
-        (plan) => plan.group === billingPlanGroup
+        (plan): plan is Models.BillingPlan => !!plan && plan.group === billingPlanGroup
     );
 
     return proPlans.sort((a, b) => a.order - b.order)[0];

src/routes/(console)/project-[region]-[project]/+layout.ts

@@ -99,7 +99,7 @@ export const load: LayoutLoad = async ({ params, depends, parent }) => {
         loadFailedInvoices(project.teamId);
     }
 
-    if (!includedInBasePlans) {
+    if (!includedInBasePlans && organizationPlan) {
         // save the custom plan to `plansInfo` cache.
         plansInfo.set(organization.billingPlanId, organizationPlan);
     }