This is probably a bug or rather shortcoming in the application you use to view the exported SVG.
I exported the person from your screenshot from yEd 3.14.2 on Java 8u45 and it displayed fine in
- Google Chrome
- Mozilla Firefox
- Gwenview (the KDE image viewer)
- Squiggle (the BATIK SVG viewer)
It did actually display the same black line as in your screenshot when viewed in
- GNU Emacs 23.3.1 and in
- Mozilla Firefox's file preview (but only in the preview)
For the technically inclined:
The culprit seems to be the definition for the person's face highlight <path id="svg1.face_highlight_3_" .../>. This path does not have a stroke attribute, indicating that it should be filled, but not framed. Seems like librsvg2 which is used in Emacs for displaying SVG documents and Firefox's file preview (which probably does not use full-fledged SVG support) cannot handle gradient-filled paths that are not framed.