If the App crashes directly after displaying the logo there is surely a problem with the database. To solve this unfortunately the database has to be deleted and recreated. To do this there are two ways: A complete new installation or only deleting the database.
Delete the App directly on iOS (with the long tap on the icon and then tapping the cross beside the icon). After this install the App from the AppStore. By doing this all data are lost, inclusive the offline Maps.
Delete only the database:
You can delete the database with iTunes. By doing this all Caches, Cache Lists and local logs are lost. But the configuration, the downloaded offline maps and the stored images will be available later. To do this make the following steps: Connect your device to iTunes and select it > Select the section “Apps” on the top and scroll down to the area where you can transfer files > Select “L4C Pro” or “L4C Lite” > Delete the three files starting this “database” using the Delete-Key.