Add robust log level handling in JVSGLoggerLogManager

The JVSGLoggerLogManager allows to customize the log level with a system
property. When an invalid log level is passed, the call currently throws
an exception and makes the whole rasterizer initialization fail, leading
to the non-availability of an SVG rasterizer throughout the whole
application lifecycle.

This change makes the system property processing more robust: when an
invalid level is used, an error is printed and the implementation falls
back to using "ERROR" as default log level. In addition, capitalization
is ignored by always making the passed value upper case. As a result of
this change, it not be possible to make the rasterizer implementation
fail with an invalid system property anymore.

Author: HeikoKlare

bundles/org.eclipse.swt.svg/src/org/eclipse/swt/svg/logging/JVSGLoggerLogManager.java

@@ -17,7 +17,17 @@
 
 public class JVSGLoggerLogManager implements LogManager {
 
-	private static final Logger.Level LEVEL = Logger.Level.valueOf(System.getProperty("org.eclipse.swt.svg.logging", "ERROR"));
+	private static final Logger.Level LEVEL = getLogLevel();
+
+	private static Logger.Level getLogLevel() {
+		try {
+			return Enum.valueOf(Logger.Level.class, System.getProperty("org.eclipse.swt.svg.logging", "ERROR").toUpperCase());			
+		} catch (IllegalArgumentException e) {
+			System.err.format("JSVGRasterizer: Invalid log level specified: %s. Defaulting to ERROR.",
+					System.getProperty("org.eclipse.swt.svg.logging")).println();
+			return Logger.Level.ERROR;
+		}
+	}
 
 	@Override
 	public Logger createLogger(String name) {