Comment 21 for bug 1046068

Attached is a quick hack to stop the known error messages if width and/or height attributes are missing (quick hack, depends on diff from comment #13 which supplies a new 'errormsg()' function that checks whether the output parses an SVG file based on the clipboard content).

Missing: stop UniConvertor failure messages from being reported back if clipboard content is parsed (inkex.py is already imported in 'uniconv_output.py' - it would be possible to init the effect with the doc, but one would first need to extract the path to the document first from 'command_format' AFAIU)