fix an empty check case.

spec/inputs/in_expression.yue

@@ -72,6 +72,8 @@ do
 			2
 			x: 3
 		}
-
+	print a in []
+	a = 1
+	print a in {}
 nil
 

spec/outputs/in_expression.lua

@@ -206,5 +206,11 @@ do
 			b = not _find_0
 		end
 	end
+	print((function()
+		local _val_0 = a
+		return false
+	end)())
+	local a = 1
+	print((false))
 end
 return nil

src/yuescript/yue_compiler.cpp

@@ -75,7 +75,7 @@ static std::unordered_set<std::string> Metamethods = {
 	"close"s // Lua 5.4
 };
 
-const std::string_view version = "0.21.7"sv;
+const std::string_view version = "0.21.8"sv;
 const std::string_view extension = "yue"sv;
 
 class CompileError : public std::logic_error {
@@ -6162,10 +6162,14 @@ class YueCompilerImpl {
 				if (unary_exp->inExp->not_) {
 					_buf << "not ("sv;
 				}
-				for (const auto& exp : tmp) {
-					_buf << exp << " == "sv << newVar;
-					if (exp != tmp.back()) {
-						_buf << " or "sv;
+				if (tmp.empty()) {
+					_buf << "false"sv;
+				} else {
+					for (const auto& exp : tmp) {
+						_buf << exp << " == "sv << newVar;
+						if (exp != tmp.back()) {
+							_buf << " or "sv;
+						}
 					}
 				}
 				if (unary_exp->inExp->not_) {
@@ -6203,10 +6207,14 @@ class YueCompilerImpl {
 					_buf << "not "sv;
 				}
 				_buf << '(';
-				for (const auto& exp : tmp) {
-					_buf << exp << " == "sv << varName;
-					if (exp != tmp.back()) {
-						_buf << " or "sv;
+				if (tmp.empty()) {
+					_buf << "false"sv;
+				} else {
+					for (const auto& exp : tmp) {
+						_buf << exp << " == "sv << varName;
+						if (exp != tmp.back()) {
+							_buf << " or "sv;
+						}
 					}
 				}
 				_buf << ')';