fix(republik-crowdfundings): Set initial value on Array.reduce to 0

Array insertPromises might be an empty array.

Setting initial value prevents error "Reduce of empty array with no initial value".

Author: patrickvenetz

packages/republik-crowdfundings/lib/scheduler/importPayments.ts

@@ -257,7 +257,7 @@ const insertPayments = async ({
     return await postfinancePaymentsTable.insert(record)
   })
 
-  return (await Promise.all(insertPromises)).reduce((a, b) => a + b)
+  return (await Promise.all(insertPromises)).reduce((a, b) => a + b, 0)
 }
 
 interface PostfinancePaymentRecord {