Don't run in NPE if application is not available in BindingTable

Before #2859
`org.eclipse.e4.ui.bindings.tests` manage to run without application
instance created/set in the global context, because
`core-test` (and not `ui-test`) was used in
org.eclipse.e4.ui.bindings.tests/test.xml.

Thus `org.eclipse.test.coretestapplication` was used to run bindings
tests, not `org.eclipse.test.uitestapplication`. Later one uses
`org.eclipse.ui.ide.workbench` application by default which runs
`E4Application.createE4Workbench()` and that one will create and set
application via `E4Workbench.getServiceContext().set(MApplication.class,
appModel);`.

For now there is no reason to change this behavior, we can simply allow
application to be null in BindingTable which should not affect its
behavior in a context that has no application defined.

Fixes #2872

Author: iloveeclipse

bundles/org.eclipse.e4.ui.bindings/src/org/eclipse/e4/ui/bindings/internal/BindingTable.java

@@ -376,7 +376,7 @@ private boolean isActive(final Binding binding) {
 			return false;
 		}
 		String identifierId = command.getId();
-		if (contributionFactory == null) {
+		if (contributionFactory == null && application != null) {
 			contributionFactory = application.getContext().get(IContributionFactory.class);
 		}
 		if (contributionFactory == null) {