if xffm is compiled with any optimization cflags, it will not generate image
preview correctly when browsing folders that contain image files. right click an
image file and select "preview" from the pop up menu, xffm reports "invalid
argument" in the status line. however, if i remove the "-O2" flag from the
makefile and rebuild xffm, the preview feature works.
the source code i use is xffm-4.2.2.tar.gz downloaded from the xfce site.

Reproducible: Always
Steps to Reproduce:
1. build xffm with ./configure and make
2. launch xffm, navigate to a folder which contains image files
3. right click an image , choose "preview" from the popup menu

Actual Results:  
xffm says "invalid argument filename" where filename is the file i choose to
preview.

Expected Results:  
xffm show the thumnail of the file.