[BUG] Handle empty string for non-required query parameter

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

openapi-generator version

v5.4.0

OpenAPI declaration file content or url

  /objectives/alerts:
    get:
      summary: Get the MultiBurnrateAlerts for the Objective
      operationId: GetMultiBurnrateAlerts
      tags:
        - objectives
      parameters:
        - in: query
          name: expr
          required: true
          schema:
            type: string
        - in: query
          name: grouping
          required: false
          schema:
            type: string
        - in: query
          name: inactive
          required: false
          schema:
            type: boolean
            default: false

It's about the last query parameter called inactive here.

The problem seems to be, that even though the parameter isn't required the code doesn't handle a non existing &inactive in the URL and instantly returns 500 internal server error

https://github.com/OpenAPITools/openapi-generator/blob/941d4845d73536473ac6ef63ebaa6e762bdf0606/modules/openapi-generator/src/main/resources/go-server/routers.mustache#L201-L209

Generation Details

docker run openapitools/openapi-generator-cli:v5.4.0

Steps to reproduce

This first one works as the parameter doesn't have an empty string but f
http://localhost:9099/api/v1/objectives/alerts?expr=&inactive=f
The second one doesn't work, as the string is "" and that results in a parse error.
http://localhost:9099/api/v1/objectives/alerts?expr=&inactive=

Here's the Go stdlib for parsing the boolean that returns a syntaxError:
https://cs.opensource.google/go/go/+/refs/tags/go1.18:src/strconv/atob.go;l=10

Related issues/PRs

Suggest a fix

Something similar to other types should be just fine. For example:
https://github.com/OpenAPITools/openapi-generator/blob/941d4845d73536473ac6ef63ebaa6e762bdf0606/modules/openapi-generator/src/main/resources/go-server/routers.mustache#L184-L191

Inspect modules/openapi-generator/src/main/resources/go-server/routers.mustache, especially the parameter handling around lines 184-209, and compare the optional boolean path with the other types. Reproduce the generated server behavior using the provided OpenAPI declaration and URLs; done means an empty optional inactive query value no longer causes a 500 parse error.