Fix association replace non-addressable panic

[SergeiSadov]

• Do only one thing
• Non breaking API changes
• Tested

What did this pull request do?

While replacing associations using an example from the docs panic occurs.

db.Model(&user).Association("Languages").Replace(Language{Name: "DE"}, languageEN)

This PR fixes this issue by asserting if the value addressable and checking for the association error later.

User Case Description

Here is the PR for the playground example: go-gorm/playground#734
This is not the obvious case, but the code should not panic in the case, but invalid value gracefully