Apply suggestions from code review

Co-authored-by: Fernando Fernández <[email protected]>

Author: yyx990803

Diff for: packages/runtime-core/src/components/BaseTransition.ts

@@ -227,7 +227,6 @@ const BaseTransitionImpl: ComponentOptions = {
               instance.update()
             }
             delete leavingHooks.afterLeave
-            oldInnerChild = undefined
           }
           return emptyPlaceholder(child)
         } else if (mode === 'in-out' && innerChild.type !== Comment) {
@@ -246,20 +245,14 @@ const BaseTransitionImpl: ComponentOptions = {
               earlyRemove()
               el[leaveCbKey] = undefined
               delete enterHooks.delayedLeave
-              oldInnerChild = undefined
             }
             enterHooks.delayedLeave = () => {
               delayedLeave()
               delete enterHooks.delayedLeave
-              oldInnerChild = undefined
             }
           }
-        } else {
-          oldInnerChild = undefined
         }
-      } else if (oldInnerChild) {
-        oldInnerChild = undefined
-      }
+      oldInnerChild = undefined
 
       return child
     }