Apply fixes from StyleCI (#185)

Author: binaryk

src/Fields/Field.php

@@ -317,7 +317,7 @@ public function resolveForShow($repository, $attribute = null)
             return;
         }
 
-        if (!$this->showCallback) {
+        if (! $this->showCallback) {
             $this->resolve($repository, $attribute);
         } elseif (is_callable($this->showCallback)) {
             tap($this->value ?? $this->resolveAttribute($repository, $attribute), function ($value) use ($repository, $attribute) {
@@ -340,7 +340,7 @@ public function resolveForIndex($repository, $attribute = null)
             return;
         }
 
-        if (!$this->indexCallback) {
+        if (! $this->indexCallback) {
             $this->resolve($repository, $attribute);
         } elseif (is_callable($this->indexCallback)) {
             tap($this->value ?? $this->resolveAttribute($repository, $attribute), function ($value) use ($repository, $attribute) {
@@ -360,7 +360,7 @@ public function resolve($repository, $attribute = null)
             return;
         }
 
-        if (!$this->resolveCallback) {
+        if (! $this->resolveCallback) {
             $this->value = $this->resolveAttribute($repository, $attribute);
         } elseif (is_callable($this->resolveCallback)) {
             tap($this->resolveAttribute($repository, $attribute), function ($value) use ($repository, $attribute) {