kin-openapi openapi3filter: unauthenticated nil-pointer panic when validating a request against a `content` parameter whose media type has no schema

kin-openapi is a Go project for handling OpenAPI files. From 0.2.0 until 0.144.0, openapi3filter.ValidateRequest can encounter a NULL-pointer-dereference denial of service when an operation declares a content parameter whose application/json media type has no schema. In openapi3filter/req_resp_decoder.go, the default defaultContentParameterDecoder dereferences mt.Schema.Value without checking whether mt.Schema is nil, even though doc.Validate() accepts the document under OpenAPI 3.0.x and 3.1.x. A single unauthenticated request supplying the parameter value can panic request validation, causing an aborted request with log growth in the common synchronous net/http path or a full process crash in integrations without recovery. This issue is fixed in version 0.144.0.