Trying to load an SVG while the JSVG rasterizer is not in the classpath
throws a ServiceConfigurationError. This error should be caught and
transformed into an SWTError, as specified by the contract of the
ImageLoader.

By catching the ServiceConfigurationError, the RASTERIZER field is
initialized with NULL. In this state, calling any method of the
SVGFileFormat class automatically throws the expected SWTError.

To reproduce, load an SVG while `org.eclipse.swt.svg` is in the
classpath, but `com.github.weisj.jsvg` is not. This call should fail
with a:

> Provider org.eclipse.swt.svg.JSVGRasterizer could not be instantiated

Due to a NoClassDefFoundError when trying to load the JSVGRasterizer
class, caused by the unresolvable dependency.