Fix "fixed cells state" when randomize board

android/gradle.properties

 org.gradle.jvmargs=-Xmx1536M
 android.useAndroidX=true
 android.enableJetifier=true
-app.versionName=0.0.11
-app.versionCode=11
+app.versionName=0.0.12
+app.versionCode=12

lib/entities/cell.dart

@@ -7,7 +7,7 @@ class Cell {
   int value;
   final int col;
   final int row;
-  final bool isFixed;
+  bool isFixed;
 
   Cell(
     @required this.value,

lib/screens/home.dart

@@ -123,6 +123,13 @@ class Home extends StatelessWidget {
       break;
     }
 
+    // Fix cells fixed states
+    for (var rowIndex = 0; rowIndex < sideLength; rowIndex++) {
+      for (var colIndex = 0; colIndex < sideLength; colIndex++) {
+        cells[rowIndex][colIndex].isFixed = (cells[rowIndex][colIndex].value != 0) ? true : false;
+      }
+    }
+
     return cells;
   }