[BUG][typescript-angular] using --model-name-prefix: if model name starts with the passed prefix, the file name is incorrect

Description

When generating code, I'm passing the --model-name-prefix "I" option in my command. This is generating all my models with the prefix 'I'.
This is working fine for all my models except 1.
The name of the model is Invoice and the generated model in code is IInvoice. This is correct, but the generated file is 'nvoice.ts'. It seems that in this case, the i is dropped from my filename. This gives an error, because in the generated service file, the import is as follows:
import { IInvoice } from '../model/invoice'

openapi-generator version

version 4.2.0

Steps to reproduce

Generate a model which has a name starting with the same letter as the --model-name-prefix value

Suggest a fix

generated filename should be: invoice.ts

Start by reproducing the TypeScript Angular generation with version 4.2.0, --model-name-prefix "I", and a model named Invoice. Inspect the generated model filename and service import; done means the model is written as invoice.ts and the generated import resolves correctly.