Better error handling

src/de/steamwar/sql/internal/SqlTypeMapper.java

@@ -32,7 +32,12 @@ public final class SqlTypeMapper<T> {
     private static final Map<Class<?>, SqlTypeMapper<?>> mappers = new IdentityHashMap<>();
 
     public static <T> SqlTypeMapper<T> getMapper(Class<?> clazz) {
-        return (SqlTypeMapper<T>) mappers.get(clazz);
+        SqlTypeMapper<T> result = (SqlTypeMapper<T>) mappers.get(clazz);
+
+        if(result == null)
+            throw new SecurityException("Unregistered mapper requested: " + clazz.getName());
+
+        return result;
     }
 
     public static <T extends Enum<T>> void ordinalEnumMapper(Class<T> type) {