Cumsum excluding some rows

I have a question linked to: Cumsum excluding current value How to apply cumsum excluding a certain customer.id? For instance:

order.id   customer.id      Apples   Peaches  Pears
1001       J Car Ltd            1       0       0
1002        Som Comp            1       2       0
1005       Richardson           0       0       1
1004       J Car Ltd            1       0       0
1003       J Car Ltd            2       0       0
1006       Richardson           1       0       1
1007        Aldridge            0       0       1
1008       J Car Ltd            0       0       1
1010        Som Comp            0       1       0

I want to apply cumsum to keep track of previous apple orders:

Fruits <- Fruits[order(Fruits$order.id), ]  #sort data
Fruits$prev_Apples<-with(Fruits, 
    ave(
        ave(Apples, customer.id, FUN=cumsum),  #get running sum per customer.id
        interaction(customer.id, order.id, drop=T), 
    FUN=max, na.rm=T) #find largest sum per index per seg
)

But I also want to exclude from my cumsum customer.id Som Comp. For him, I want the prev_Apples column to be equal to 0:

order id    customer id     Apples  Peaches Pears   Prev_Apples
1001      J Car Ltd             1           0       0       0
1002      Som Comp            **1**         2       0       0
1003      J Car Ltd             2           0       0       1
1004      J Car Ltd             1           0       0       3
1005      Richards              0           0       1       0
1006      Richards              1           0       1       0
1007      Aldridge              0           0       1       0
1008      J Car Ltd             0           0       1       4
1010      Som Comp              1           0       0     **0**

So I thought to add this line of code:

if(Fruits$customer id =='NULL'){
Prev_Apples = 0
return (Fruits$customer id)
}

But of course I get the error: “the condition has length > 1 and only the first element will be used”

I understood why I get the error, but how can I avoid it? Thanks in advance.