Fix some conversion problems

src/main/java/be/seeseepuff/pcinv/meta/AssetProperty.java

@@ -99,7 +99,7 @@ public class AssetProperty {
                 .setter((obj, value) -> {
                     try {
                         property.setAccessible(true);
-                        property.set(obj, value);
+                        property.set(obj, Converters.convert(value, property.getType()));
                     } catch (IllegalAccessException e) {
                         throw new RuntimeException(e);
                     }

src/main/java/be/seeseepuff/pcinv/meta/Converters.java

@@ -0,0 +1,66 @@
+package be.seeseepuff.pcinv.meta;
+
+import lombok.experimental.UtilityClass;
+
+/**
+ * Utility class for converting values to different types.
+ */
+@UtilityClass
+public class Converters {
+    /**
+     * Converts a value to the specified target type.
+     *
+     * @param value  The value to convert.
+     * @param target The target class to convert the value to.
+     * @return The converted value, or null if conversion is not possible.
+     */
+    public static Object convert(Object value, Class<?> target) {
+        if (value == null) {
+            return null;
+        }
+        if (target.isInstance(value)) {
+            return value; // No conversion needed
+        }
+        if (value instanceof Long longValue) {
+            return convertLong(longValue, target);
+        }
+        if (value instanceof Integer intValue) {
+            return convertInteger(intValue, target);
+        }
+        throw new ClassCastException("Cannot convert " + value.getClass().getName() + " to " + target.getName());
+    }
+
+    /**
+     * Converts a Long value to the specified target type.
+     *
+     * @param value  The Long value to convert.
+     * @param target The target class to convert the value to.
+     * @return The converted value, or throws ClassCastException if conversion is not possible.
+     */
+    private static Object convertLong(Long value, Class<?> target) {
+        if (target == Long.class || target == long.class) {
+            return value; // No conversion needed
+        }
+        if (target == Integer.class || target == int.class) {
+            return value.intValue();
+        }
+        throw new ClassCastException("Cannot convert " + value.getClass().getName() + " to " + target.getName());
+    }
+
+    /**
+     * Converts an Integer value to the specified target type.
+     *
+     * @param value  The Integer value to convert.
+     * @param target The target class to convert the value to.
+     * @return The converted value, or throws ClassCastException if conversion is not possible.
+     */
+    private static Object convertInteger(Integer value, Class<?> target) {
+        if (target == Integer.class || target == int.class) {
+            return value; // No conversion needed
+        }
+        if (target == Long.class || target == long.class) {
+            return value.longValue();
+        }
+        throw new ClassCastException("Cannot convert " + value.getClass().getName() + " to " + target.getName());
+    }
+}