fix: item data type wrong in iteration (#19709)

web/app/components/workflow/nodes/_base/components/variable/utils.ts

   const isSystem = isSystemVar(valueSelector)
 
   const targetVar = isSystem ? beforeNodesOutputVars.find(v => v.isStartNode) : beforeNodesOutputVars.find(v => v.nodeId === outputVarNodeId)
+
   if (!targetVar)
     return VarType.string
 
     arrayType = curr.find((v: any) => v.variable === (valueSelector).join('.'))?.type
   }
   else {
-    for (let i = 1; i < valueSelector.length - 1; i++) {
+    for (let i = 1; i < valueSelector.length; i++) {
       const key = valueSelector[i]
-      const isLast = i === valueSelector.length - 2
+      const isLast = i === valueSelector.length - 1
       curr = Array.isArray(curr) ? curr.find(v => v.variable === key) : []
 
       if (isLast)