Fix empty preconditions not firing

lib/local-cache.ts

@@ -158,7 +158,8 @@ async function fetchPresets(): Promise<Preset[]> {
     }
 
     const events = preset["events"] || {};
-    let precondition;
+    let precondition = true as Expression;
+    if (preset["precondition"]) {
       try {
         precondition = parse(preset["precondition"]);
       } catch (error) {
@@ -167,6 +168,7 @@ async function fetchPresets(): Promise<Preset[]> {
 
       // Simplify expression
       precondition = expression.evaluate(precondition);
+    }
 
     const _provisions = preset["provisions"] || [];