Fix SWT Resources disposal runtime warnings in installer

Method createBodyContent calls clearDisposable which empties the
disposables collections without actually disposing them leading to
dangling references.
Make the method actually dispose all disposables before clearing ensures
that all resources are actually freed.

Author: akurtakov

openchrom/plugins/net.openchrom.installer.ui/src/net/openchrom/installer/ui/wizards/PluginDiscoveryWizardMainPage.java

@@ -286,17 +286,16 @@ public void pluginDescriptorKindVisibilityUpdated() {
 	public void dispose() {
 
 		super.dispose();
-		for(Resource resource : disposables) {
-			resource.dispose();
-		}
 		clearDisposables();
 		if(discovery != null) {
 			discovery.dispose();
 		}
 	}
 
 	private void clearDisposables() {
-
+		for(Resource resource : disposables) {
+			resource.dispose();
+		}
 		disposables.clear();
 		h1Font = null;
 		h2Font = null;