fix: check for nullish prop instead of falsy (#12)

Author: MattieBelt

.changeset/smart-months-provide.md

@@ -0,0 +1,5 @@
+---
+'@strapi/pack-up': patch
+---
+
+Check for nullish build options and don't fallback for falsy values

src/node/core/config.ts

@@ -130,7 +130,7 @@ type ConfigProperty<T> = T | ConfigPropertyResolver<T>;
 
 /** @internal */
 export function resolveConfigProperty<T>(prop: ConfigProperty<T> | undefined, initialValue: T): T {
-  if (!prop) {
+  if (prop === undefined || prop === null) {
     return initialValue;
   }