fix: do not treat falsy values like 0 and false as undefined

packages/experiment-core/src/evaluation/evaluation.ts

@@ -116,7 +116,7 @@ export class EvaluationEngine {
     // We need special matching for null properties and set type prop values
     // and operators. All other values are matched as strings, since the
     // filter values are always strings.
-    if (!propValue) {
+    if (propValue === undefined || propValue === null) {
       return this.matchNull(condition.op, condition.values);
     } else if (this.isSetOperator(condition.op)) {
       const propValueStringList = this.coerceStringArray(propValue);

packages/experiment-core/src/evaluation/select.ts

@@ -11,7 +11,7 @@ export const select = (
     }
     selectable = (selectable as Record<string, unknown>)[selectorElement];
   }
-  if (!selectable) {
+  if (selectable === undefined || selectable === null) {
     return undefined;
   } else {
     return selectable;