Skip the method PluginsTab::performApply until after activation

If this method (or part of it) is run before the tab has been activated
then the default configuration passed as parameter will be modified and
incorrect values will be introduced.

This commit fixes a regression introduced in
98a5865

Fixes #1250

ui/org.eclipse.pde.ui/src/org/eclipse/pde/ui/launcher/PluginsTab.java

@@ -199,12 +199,13 @@ public void setDefaults(ILaunchConfigurationWorkingCopy configuration) {
 
 	@Override
 	public void performApply(ILaunchConfigurationWorkingCopy configuration) {
+		if (!fActivated) {
+			return;
+		}
 		int index = fSelectionCombo.getSelectionIndex();
 		configuration.setAttribute(IPDELauncherConstants.USE_DEFAULT, index == DEFAULT_SELECTION);
 		configuration.setAttribute(IPDELauncherConstants.USE_CUSTOM_FEATURES, index == FEATURE_SELECTION);
-		if (fActivated) {
 			fBlock.performApply(configuration);
-		}
 		// clear default values for auto-start and start-level if default
 		String autoText = fDefaultAutoStart.getText();
 		if (Boolean.toString(false).equals(autoText)) {