check null safety

lib/helpers/theme.dart

@@ -20,8 +20,10 @@ const TextStyle labelStyleMM = TextStyle(
     fontFamily: "Myanmar3");
 const TextStyle subMenuStyle =
     TextStyle(fontSize: 14, color: Colors.white, fontWeight: FontWeight.w500);
-const TextStyle subMenuStyleMM =
-    TextStyle(fontSize: 14, color: Colors.white, fontWeight: FontWeight.w500,
+const TextStyle subMenuStyleMM = TextStyle(
+    fontSize: 14,
+    color: Colors.white,
+    fontWeight: FontWeight.w500,
     fontFamily: "Myanmar3");
 
 const TextStyle welcomeLabelStyle =
@@ -31,11 +33,10 @@ const TextStyle welcomeSubLabelStyle =
 const TextStyle siginButtonStyle =
     TextStyle(fontSize: 16, color: Colors.white, fontWeight: FontWeight.w500);
 
-
 TextStyle newLabelStyle(
-    {Color color,
-    double fontSize,
-    FontWeight fontWeight,
+    {Color? color,
+    double? fontSize,
+    FontWeight? fontWeight,
     bool underline = false}) {
   return TextStyle(
       fontSize: fontSize == null ? 14 : fontSize,
@@ -45,9 +46,9 @@ TextStyle newLabelStyle(
 }
 
 TextStyle newLabelStyleMM(
-    {Color color,
-    double fontSize,
-    FontWeight fontWeight,
+    {Color? color,
+    double? fontSize,
+    FontWeight? fontWeight,
     bool underline = false}) {
   return TextStyle(
       fontSize: fontSize == null ? 13 : fontSize,
@@ -59,8 +60,8 @@ TextStyle newLabelStyleMM(
 
 const TextStyle photoLabelStyle =
     TextStyle(color: Colors.black, fontSize: 13.0);
-const TextStyle photoLabelStyleMM = TextStyle(
-    color: Colors.black, fontSize: 13.0, fontFamily: "Myanmar3");
+const TextStyle photoLabelStyleMM =
+    TextStyle(color: Colors.black, fontSize: 13.0, fontFamily: "Myanmar3");
 const TextStyle textStyle =
     TextStyle(fontSize: 14, color: Colors.black87, fontWeight: FontWeight.w500);
 const TextStyle textStyleOdd = TextStyle(