R514: problem with quick viewer and plugin

[uwee]

There is a problem with quick viewer and a wlx-plugin i use; steps to reproduce:

- installation of imagine.wlx-plugin (a very good and fast viewer of images)
- higher priority as normal Image/Multimedia viewer
- highlighting an image (jpg)
- quick view window opens but does not show anything (only blank = grey background)
- only by changing the size of the window or by changing the viewer category to another one and back to plugin the normal picture is shown

This behaviour occurs only with the first picture shown; when quick view is not closed one can change the highlighted file and it is viewed correctly with the plugin