Fix crash of list related functions (vesoft-inc#2467)

small delete

Co-authored-by: kyle.cao <[email protected]>

src/common/function/FunctionManager.cpp

@@ -2033,8 +2033,11 @@ FunctionManager::FunctionManager() {
           return v.vid;
         }
         case Value::Type::LIST: {
-          const auto &listVal = args[0].get().getList();
-          auto &lastVal = listVal.values.back();
+          const auto &listVal = args[0].get().getList().values;
+          if (listVal.empty()) {
+            return Value::kNullBadType;
+          }
+          auto &lastVal = listVal.back();
           if (lastVal.isEdge()) {
             return lastVal.getEdge().dst;
           } else if (lastVal.isVertex()) {
@@ -2167,7 +2170,8 @@ FunctionManager::FunctionManager() {
           return Value::kNullValue;
         }
         case Value::Type::LIST: {
-          return args[0].get().getList().values.front();
+          const auto &items = args[0].get().getList().values;
+          return items.empty() ? Value::kNullValue : items.front();
         }
         default: {
           return Value::kNullBadType;
@@ -2186,7 +2190,8 @@ FunctionManager::FunctionManager() {
           return Value::kNullValue;
         }
         case Value::Type::LIST: {
-          return args[0].get().getList().values.back();
+          const auto &items = args[0].get().getList().values;
+          return items.empty() ? Value::kNullValue : items.back();
         }
         default: {
           return Value::kNullBadType;

tests/tck/features/yield/return.feature

@@ -14,6 +14,13 @@ Feature: Return. A standalone return sentence is actually a yield sentence
     Then the result should be, in any order:
       | sum |
       | 2   |
+    When executing query:
+      """
+      RETURN last(LIST[]) AS a, head(LIST[]) AS b
+      """
+    Then the result should be, in any order:
+      | a    | b    |
+      | NULL | NULL |
     When executing query:
       """
       RETURN 1- -1 AS sub
@@ -26,6 +33,11 @@ Feature: Return. A standalone return sentence is actually a yield sentence
       RETURN 1--1 AS sub
       """
     Then a SyntaxError should be raised at runtime: syntax error near `--'
+    When executing query:
+      """
+      MATCH (v:player) RETURN none_direct_dst(LIST[]) AS a
+      """
+    Then a SemanticError should be raised at runtime: Type error `none_direct_dst([])'
     When executing query:
       """
       RETURN  [2,3 ] - [3] AS sub