Various code cleanup.

app/Http/Controllers/Report/BalanceController.php

@@ -64,7 +64,7 @@ class BalanceController extends Controller
      * @param Carbon     $start
      * @param Carbon     $end
      *
-     * @return mixed|string
+     * @return string
      */
     public function general(Collection $accounts, Carbon $start, Carbon $end)
     {

app/Http/Controllers/Report/BillController.php

@@ -40,6 +40,9 @@ class BillController extends Controller
      * @param Collection $accounts
      * @param Carbon     $start
      * @param Carbon     $end
+     *
+     * @return mixed|string
+     * @throws \JsonException
      */
     public function overview(Collection $accounts, Carbon $start, Carbon $end)
     {   // chart properties for cache:

app/Http/Controllers/Report/BudgetController.php

@@ -160,7 +160,7 @@ class BudgetController extends Controller
      * @param Carbon     $start
      * @param Carbon     $end
      *
-     * @return array|string
+     * @return string
      */
     public function avgExpenses(Collection $accounts, Collection $budgets, Carbon $start, Carbon $end)
     {
@@ -281,7 +281,7 @@ class BudgetController extends Controller
      * @param Carbon     $start
      * @param Carbon     $end
      *
-     * @return mixed|string
+     * @return string
      */
     public function general(Collection $accounts, Carbon $start, Carbon $end)
     {
@@ -369,7 +369,7 @@ class BudgetController extends Controller
      * @param Carbon     $start
      * @param Carbon     $end
      *
-     * @return array|string
+     * @return string
      */
     public function topExpenses(Collection $accounts, Collection $budgets, Carbon $start, Carbon $end)
     {

app/Http/Controllers/Report/CategoryController.php

@@ -274,7 +274,7 @@ class CategoryController extends Controller
      * @param Carbon     $start
      * @param Carbon     $end
      *
-     * @return array|string
+     * @return string
      */
     public function avgExpenses(Collection $accounts, Collection $categories, Carbon $start, Carbon $end)
     {
@@ -326,7 +326,7 @@ class CategoryController extends Controller
      * @param Carbon     $start
      * @param Carbon     $end
      *
-     * @return array|string
+     * @return string
      */
     public function avgIncome(Collection $accounts, Collection $categories, Carbon $start, Carbon $end)
     {
@@ -685,7 +685,7 @@ class CategoryController extends Controller
      * @param Carbon     $start
      * @param Carbon     $end
      *
-     * @return array|string
+     * @return string
      */
     public function topExpenses(Collection $accounts, Collection $categories, Carbon $start, Carbon $end)
     {
@@ -735,7 +735,7 @@ class CategoryController extends Controller
      * @param Carbon     $start
      * @param Carbon     $end
      *
-     * @return array|string
+     * @return string
      */
     public function topIncome(Collection $accounts, Collection $categories, Carbon $start, Carbon $end)
     {

app/Http/Controllers/Report/DoubleController.php

@@ -74,7 +74,7 @@ class DoubleController extends Controller
      * @param Carbon     $start
      * @param Carbon     $end
      *
-     * @return array|string
+     * @return string
      */
     public function avgExpenses(Collection $accounts, Collection $doubles, Carbon $start, Carbon $end)
     {
@@ -126,7 +126,7 @@ class DoubleController extends Controller
      * @param Carbon     $start
      * @param Carbon     $end
      *
-     * @return array|string
+     * @return string
      */
     public function avgIncome(Collection $accounts, Collection $doubles, Carbon $start, Carbon $end)
     {
@@ -422,7 +422,7 @@ class DoubleController extends Controller
      * @param Carbon     $start
      * @param Carbon     $end
      *
-     * @return array|string
+     * @return string
      */
     public function topExpenses(Collection $accounts, Collection $doubles, Carbon $start, Carbon $end)
     {
@@ -472,7 +472,7 @@ class DoubleController extends Controller
      * @param Carbon     $start
      * @param Carbon     $end
      *
-     * @return array|string
+     * @return string
      */
     public function topIncome(Collection $accounts, Collection $doubles, Carbon $start, Carbon $end)
     {

app/Http/Controllers/Report/TagController.php

@@ -268,7 +268,7 @@ class TagController extends Controller
      * @param Carbon     $start
      * @param Carbon     $end
      *
-     * @return array|string
+     * @return string
      */
     public function avgExpenses(Collection $accounts, Collection $tags, Carbon $start, Carbon $end)
     {
@@ -320,7 +320,7 @@ class TagController extends Controller
      * @param Carbon     $start
      * @param Carbon     $end
      *
-     * @return array|string
+     * @return string
      */
     public function avgIncome(Collection $accounts, Collection $tags, Carbon $start, Carbon $end)
     {
@@ -480,7 +480,7 @@ class TagController extends Controller
      * @param Carbon     $start
      * @param Carbon     $end
      *
-     * @return array|string
+     * @return string
      */
     public function topExpenses(Collection $accounts, Collection $tags, Carbon $start, Carbon $end)
     {
@@ -530,7 +530,7 @@ class TagController extends Controller
      * @param Carbon     $start
      * @param Carbon     $end
      *
-     * @return array|string
+     * @return string
      */
     public function topIncome(Collection $accounts, Collection $tags, Carbon $start, Carbon $end)
     {