Flatlist keyExtractor returns "TypeError: null is not an object" when data is null

I have the following React Native Flatlist:

<FlatList
            data={dataOnDevice}
            renderItem={({ item }) => {
              return (
                <RowItem
                  id={item.id}
                  key={item.id}
                  text={`ID: ${item.id} Name: ${item.name} Group: ${item.group}`}
                  onPress={() => {
                    navigation.pop();
                  }}
                  rightIcon={
                    <View style={styles.icon}>
                      <Entypo name="trash" size={20} color={colors.white} />
                    </View>
                  }
                />
              );
            }}
            ItemSeparatorComponent={() => <RowSeparator />}
            ListFooterComponent={() => (
              <View style={{ paddingBottom: insets.bottom }} />
            )}
            ListEmptyComponent={() => listEmptyComponent()}
            keyExtractor={(item) => item.id.toString()}
          />

This works fine when I have data in the list but when dataOnDevice is null, I get an error:

TypeError: null is not an object (evaluating 'item.id.toString')

This has happened after a refactoring which causes dataOnDevice to be null. My understanding is that ListEmptyComponent should be able to handle that...

How can I prevent this error with the keyExtractor?

For now I found a way around this by adding:

keyExtractor={(item) => {              
  if (item !== "") {              
    item.id.toString();             
  }            
}}

But I'm open to any cleaner way of handling it...