set a temporary filename before saving it. Fix #541

                    
|Q            |A   |
|---          |--- |
|Bug Fix?     |y   |
|New Feature? |n   |
|BC Breaks?   |n   |
|Deprecations?|n   |
|Tests Pass?  |y   |
|Fixed Tickets|541 |
|License      |LGPL|
|Doc PR       |    |