refactor(decorators): simplify logic in the three new decorators

Remove unneeded local variables, and let the three new decorators return `TaskStatus.Failure` if
they have no child

Author: JesseTG

Assets/FluidBehaviorTree/Runtime/Decorators/RepeatForever.cs

@@ -5,7 +5,7 @@
 namespace CleverCrow.Fluid.BTs.Decorators {
     public class RepeatForever : DecoratorBase {
         protected override TaskStatus OnUpdate () {
-            Child?.Update();
+            Child.Update();
             return TaskStatus.Continue;
         }
     }

Assets/FluidBehaviorTree/Runtime/Decorators/RepeatUntilFailure.cs

@@ -5,19 +5,11 @@
 namespace CleverCrow.Fluid.BTs.Decorators {
     public class RepeatUntilFailure : DecoratorBase {
         protected override TaskStatus OnUpdate () {
-            if (Child == null) {
+            if (Child.Update() == TaskStatus.Failure) {
                 return TaskStatus.Failure;
             }
-
-            var childStatus = Child.Update();
-            var status = childStatus;
-
-            if (status == TaskStatus.Failure) {
-                return TaskStatus.Failure;
-            }
-            else {
-                return TaskStatus.Continue;
-            }
+            
+            return TaskStatus.Continue;
         }
     }
 }

Assets/FluidBehaviorTree/Runtime/Decorators/RepeatUntilSuccess.cs

@@ -5,19 +5,11 @@
 namespace CleverCrow.Fluid.BTs.Decorators {
     public class RepeatUntilSuccess : DecoratorBase {
         protected override TaskStatus OnUpdate () {
-            if (Child == null) {
+            if (Child.Update() == TaskStatus.Success) {
                 return TaskStatus.Success;
             }
 
-            var childStatus = Child.Update();
-            var status = childStatus;
-
-            if (status == TaskStatus.Success) {
-                return TaskStatus.Success;
-            }
-            else {
-                return TaskStatus.Continue;
-            }
+            return TaskStatus.Continue;
         }
     }
 }