fix: solve issue that promise all is not working when array size is 0

Source/Concurrency/Promise/Composition/PromiseAll.swift

@@ -30,7 +30,7 @@ extension Promise where
             promiseReturn.resolve(values)
         }
 
-        promises.forEach { promise in
+        for promise in promises {
             promise.subscribe(
                 queue: promise.queue,
                 onResolved: { _ in resolve() },
@@ -39,6 +39,10 @@ extension Promise where
             )
         }
 
+        if promises.isEmpty {
+            resolve()
+        }
+
         return promiseReturn
     }