Fix the issue of segmentation fault when the pattern of a mbe is not setted. For Skia graphic engine, a mbe does not always have a pattern. For example, a color paint does not set a pattern on a mbe for a shape. So, we check if pattern is setted before accessing it.

madbutterfly for Debian
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<possible notes regarding this package - if none, delete this file>

 -- Ben Lau <benlau@visionware.com.hk>  Thu, 09 Apr 2009 20:00:10 +0800