Fix NPE in EclipseXmlFormatterStepImpl (diffplug#489)

The method EclipseXmlFormatterStepImpl used the return value of
SpotlessEclipseFramework.setup() ir order to take decisions whether
or not to initialize.
This introduced a race condition, which is fixed by making the method
synchronized.
Also removed another empty if-statement in GrEclipseFormatterStepImpl
which also called SpotlessEclipseFramework.setup()

_ext/eclipse-groovy/src/main/java/com/diffplug/spotless/extra/eclipse/groovy/GrEclipseFormatterStepImpl.java

@@ -55,14 +55,14 @@ public class GrEclipseFormatterStepImpl {
 	private final boolean ignoreFormatterProblems;
 
 	public GrEclipseFormatterStepImpl(final Properties properties) throws Exception {
-		if (SpotlessEclipseFramework.setup(
+		SpotlessEclipseFramework.setup(
 				config -> {
 					config.applyDefault();
 					config.useSlf4J(GrEclipseFormatterStepImpl.class.getPackage().getName());
 				},
 				plugins -> {
 					plugins.add(new GroovyCoreActivator());
-				})) {}
+				});
 		PreferenceStore preferences = createPreferences(properties);
 		preferencesStore = new FormatterPreferencesOnStore(preferences);
 		ignoreFormatterProblems = Boolean.parseBoolean(properties.getProperty(IGNORE_FORMATTER_PROBLEMS, "false"));

_ext/eclipse-wtp/src/main/java/com/diffplug/spotless/extra/eclipse/wtp/EclipseXmlFormatterStepImpl.java

@@ -67,7 +67,7 @@ public EclipseXmlFormatterStepImpl(Properties properties) throws Exception {
 		xmlAdapterFactory = new ModelQueryAdapterFactoryForXML();
 	}
 
-	private static void setupFramework(boolean resolveExternalURI) throws BundleException {
+	private synchronized static void setupFramework(boolean resolveExternalURI) throws BundleException {
 		if (SpotlessEclipseFramework.setup(
 				config -> {
 					config.applyDefault();