refactor: gate auto ref injection by children arity

Author: zombieJ

src/CSSMotion.tsx

@@ -253,7 +253,9 @@ export function genCSSMotion(config: CSSMotionConfig) {
         return nextMotionChildren;
       }, [idRef.current]) as React.ReactElement;
 
-      if (supportNodeRef(motionChildren)) {
+      const shouldAutoInjectRef = children?.length < 2;
+
+      if (shouldAutoInjectRef && supportNodeRef(motionChildren)) {
         const originNodeRef = getNodeRef(motionChildren);
 
         if (originNodeRef !== nodeRef) {

src/CSSMotionList.tsx

@@ -174,7 +174,9 @@ export function genCSSMotionList(
                   }
                 }}
               >
-                {(props, ref) => children({ ...props, index }, ref)}
+                {children.length < 2
+                  ? props => children({ ...props, index }, undefined as any)
+                  : (props, ref) => children({ ...props, index }, ref)}
               </CSSMotion>
             );
           })}