MAGETWO-93305: Broken upgrade to 2.3 due to changed data type for minify_exclude

- adding trim

Author: cpartica

lib/internal/Magento/Framework/View/Asset/Minification.php

@@ -164,7 +164,13 @@ private function getMinificationExcludeValues($key)
         $configValues = $this->scopeConfig->getValue($key, $this->scope) ?? [];
         //compatibility fix for type change from new line separated string values to array
         if (!is_array($configValues)) {
-            $configValues = explode("\n", $configValues);
+            $configValuesFromString = [];
+            foreach (explode("\n", $configValues) as $exclude) {
+                if (trim($exclude) != '') {
+                    $configValuesFromString[] = trim($exclude);
+                }
+            }
+            $configValues = $configValuesFromString;
         }
         return array_values($configValues);
     }

lib/internal/Magento/Framework/View/Test/Unit/Asset/MinificationTest.php

@@ -245,8 +245,9 @@ public function testGetExcludesTinyMceAsString(string $value, array $expectedVal
     public function getExcludesTinyMceAsStringDataProvider()
     {
         return [
-            ["/tiny_mce/\n/tiny_mce2/", ['/tiny_mce/', '/tiny_mce2/']],
+            ["/tiny_mce/  \n  /tiny_mce2/", ['/tiny_mce/', '/tiny_mce2/']],
             ['/tiny_mce/', ['/tiny_mce/']],
+            [' /tiny_mce/', ['/tiny_mce/']],
         ];
     }
 }