Incorporate Review Comments

Author: BeckerWdf

bundles/org.eclipse.e4.ui.css.swt.theme/src/org/eclipse/e4/ui/css/swt/internal/theme/Theme.java

@@ -46,7 +46,12 @@ public String getOsVersion() {
 
 	@Override
 	public boolean isDark() {
-		return Boolean.parseBoolean(isDark);
+		if (isDark == null) {
+			// fallback for themes that don't yet set the "isDark" attribute
+			return id.contains("dark");
+		} else {
+			return Boolean.parseBoolean(isDark);
+		}
 	}
 
 	public void setIsDark(String isDark) {

bundles/org.eclipse.e4.ui.css.swt.theme/src/org/eclipse/e4/ui/css/swt/internal/theme/ThemeEngine.java

@@ -567,8 +567,8 @@ private String getPreferenceThemeId() {
 		return getPreferences().get(THEMEID_KEY, null);
 	}
 
-	private boolean getPreferenceThemeIsDark() {
-		return getPreferences().getBoolean(THEME_IS_DARK_KEY, false);
+	private boolean getPreferenceThemeIsDark(boolean fallback) {
+		return getPreferences().getBoolean(THEME_IS_DARK_KEY, fallback);
 	}
 
 	private IEclipsePreferences getPreferences() {
@@ -618,7 +618,7 @@ public void restore(String alternateTheme) {
 				 * this case want to fall back to respect whether that previous choice was dark
 				 * or not. https://github.com/eclipse-platform/eclipse.platform.ui/issues/2776
 				 */
-				overrideWithDarkTheme = getPreferenceThemeIsDark();
+				overrideWithDarkTheme = getPreferenceThemeIsDark(prefThemeId.contains("dark"));
 			} else {
 				/*
 				 * No previous theme selection in preferences. In this case check if the system