[OrderBundle] Fixed #1187. Don't generate order number if it exists

This fixes #1187 - order number should not be re-generated if it's already assigned

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #1187
| License       | MIT
| Doc PR        | -