Fix extra line with Dart 3.7 syntax (#1478)

Since this package is using 3.6, you can't see the result here
Verified with a one-off in this package and another package to make
sure nothing breaks

Author: kevmoo

json_serializable/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 6.9.4
+
+- Fix extra line being generated when targetting Dart 3.7 package.
+
 ## 6.9.3
 
 - Error out if the target package does not have a language version of `3.0` or 

json_serializable/lib/src/decode_helper.dart

@@ -317,27 +317,18 @@ _ConstructorData _writeConstructorInvocation(
       '$className'
       '${genericClassArguments(classElement, false)}'
       '$constructorExtra(',
-    );
-  if (constructorArguments.isNotEmpty) {
-    buffer
-      ..writeln()
-      ..writeAll(constructorArguments.map((paramElement) {
-        final content =
-            deserializeForField(paramElement.name, ctorParam: paramElement);
-        return '      $content,\n';
-      }));
-  }
-  if (namedConstructorArguments.isNotEmpty) {
-    buffer
-      ..writeln()
-      ..writeAll(namedConstructorArguments.map((paramElement) {
-        final value =
-            deserializeForField(paramElement.name, ctorParam: paramElement);
-        return '      ${paramElement.name}: $value,\n';
-      }));
-  }
-
-  buffer.write(')');
+    )
+    ..writeAll(constructorArguments.map((paramElement) {
+      final content =
+          deserializeForField(paramElement.name, ctorParam: paramElement);
+      return '      $content,\n';
+    }))
+    ..writeAll(namedConstructorArguments.map((paramElement) {
+      final value =
+          deserializeForField(paramElement.name, ctorParam: paramElement);
+      return '      ${paramElement.name}: $value,\n';
+    }))
+    ..write(')');
 
   usedCtorParamsAndFields.addAll(remainingFieldsForInvocationBody);
 

json_serializable/pubspec.yaml

@@ -1,5 +1,5 @@
 name: json_serializable
-version: 6.9.3
+version: 6.9.4
 description: >-
   Automatically generate code for converting to and from JSON by annotating
   Dart classes.