Fix: lexer string token

src/Lua/CodeAnalysis/Syntax/Lexer.cs

@@ -299,7 +299,6 @@ public ref struct Lexer
         {
             var quote = c1;
             var stringStartOffset = offset;
-            Advance(1);
 
             while (span.Length > offset)
             {

tests/Lua.Tests/LexerTests.cs

@@ -67,6 +67,7 @@ public class LexerTests
     }
 
     [Test]
+    [TestCase("\"\"")]
     [TestCase("\"hello\"")]
     [TestCase("\"1.23\"")]
     [TestCase("\"1-2-3-4-5\"")]