eclipse plugin: let's return the first Workbench Window...

...if we have any rather then the active one that might be 'null'

utils/java/eclipse_plugin/src/wesnoth_eclipse_plugin/utils/WorkspaceUtils.java

@@ -54,6 +54,8 @@ public class WorkspaceUtils
 	}
 	public static IWorkbenchWindow getWorkbenchWindow()
 	{
-		return Activator.getDefault().getWorkbench().getActiveWorkbenchWindow();
+		if (Activator.getDefault().getWorkbench().getWorkbenchWindowCount() == 0)
+			return null;
+		return Activator.getDefault().getWorkbench().getWorkbenchWindows()[0];
 	}
 }