fix system font logic

lib/helpers/extensions/scheme_to_theme.dart

@@ -1,7 +1,7 @@
 import "package:flutter/material.dart";
 
 extension SchemeToTheme on ColorScheme {
-  ThemeData getTheme(bool useDefaultFont) => .from(colorScheme: this).copyWith(
+  ThemeData getTheme(bool useSystemFont) => .from(colorScheme: this).copyWith(
     cardTheme: .new(color: primaryContainer),
     popupMenuTheme: .new(
       shape: RoundedRectangleBorder(borderRadius: .circular(16)),
@@ -11,12 +11,12 @@ extension SchemeToTheme on ColorScheme {
       titleSpacing: 0,
       backgroundColor: surfaceContainerLow,
     ),
-    textTheme: useDefaultFont
-        ? null
-        : ThemeData(
+    textTheme: useSystemFont
+        ? ThemeData(
             fontFamilyFallback: ["sans", "emoji"],
             brightness: brightness,
-          ).textTheme,
+          ).textTheme
+        : null,
     inputDecorationTheme: const InputDecorationTheme(
       border: OutlineInputBorder(),
     ),