Please describe the problem:
When saving a graph as an image and entering the wrong file extension for the image file (e.g. "graph.png" whereas SVG was chosen as the output format), a warning pops up notifying you that the extension does not match the output format. When pressing no on that warning, the whole "Save As" dialog quits, whereas it should just stay opened and users should just get the opportunity to change the filename. Unexpected behavior.

Steps to reproduce:
1. Make any graph in Gnumeric
2. Select Graph by clicking on it
3. Press right mouse button and select "Save As Image"
4. Select in the "Save As" dialog box, the output format (using the combo box left below), e.g. "SVG"
4. Then, type in the filename, with an extension that does not fit the output format, e.g. "graph.png"
5. Press "Save"
6. The following warning dialog box pops up: "The given file extension does not match the chosen file type. Do you want to use this name anyway?"
7. Choose the No option: "No"
8. "Save As" dialog box now quits altogether

Actual results:
The "Save As" dialog box quits after pressing the "no" button on the warning dialog box "The given file extension does not match the chosen file type. Do you want to use this name anyway?". 

Expected results:
It is unexpected behaviour, since after pressing the "no" button on the dialog box displaying "The given file extension does not match the chosen file type. Do you want to use this name anyway?", the "Save As" dialog box should remain open and user should be given the opportunity to just change the extension instead of having to reopen the "Save As" dialog box and retyping the whole name.


Does this happen every time?
Yes. Any graph, any time.

Other information: