Correctly set the category for test exercises...

lib/models/exercises/exercise.dart

@@ -82,6 +82,7 @@ class Exercise {
     this.muscles = muscles ?? [];
     if (category != null) {
       this.categoryObj = category;
+      this.categoryId = category.id;
     }
   }
 

test_data/exercises.dart

@@ -39,7 +39,6 @@ final exercise1 = Exercise(
   name: 'test exercise 1',
   description: 'add clever text',
   category: category1,
-  categoryId: 1,
   muscles: [muscle1, muscle2],
   musclesSecondary: [muscle3],
   equipment: [equipment1, equipment2],
@@ -52,7 +51,6 @@ final exercise2 = Exercise(
   name: 'test exercise 2',
   description: 'Lorem ipsum etc',
   category: category2,
-  categoryId: 2,
   muscles: [muscle1],
   musclesSecondary: [muscle2],
   equipment: [equipment2],
@@ -65,7 +63,6 @@ final exercise3 = Exercise(
   name: 'test exercise 3',
   description: 'The man in black fled across the desert, and the gunslinger followed',
   category: category3,
-  categoryId: 3,
   muscles: [muscle1],
   musclesSecondary: [muscle2],
   equipment: [equipment2],