MAGETWO-33618: Merchant isn't redirected to correspondent option if wants to enable Dashboard charts

- fixed code style

Author: arkadiych

app/code/Magento/Backend/Block/Dashboard.php

@@ -31,11 +31,11 @@ protected function _prepareLayout()
 
         $this->addChild('sales', 'Magento\Backend\Block\Dashboard\Sales');
 
-        if ($this->_scopeConfig->getValue(
+        $isEnabledCharts = $this->_scopeConfig->getValue(
             self::XML_PATH_ENABLE_CHARTS,
             \Magento\Store\Model\ScopeInterface::SCOPE_STORE
-        )
-        ) {
+        );
+        if ($isEnabledCharts) {
             $block = $this->getLayout()->createBlock('Magento\Backend\Block\Dashboard\Diagrams');
         } else {
             $block = $this->getLayout()->createBlock(