Fix eslint errors (#279)

Author: Murderlon

lib/stores/S3Store.js

@@ -132,14 +132,17 @@ class S3Store extends DataStore {
             },
         };
 
-        if (file.upload_length !== undefined)
+        if (file.upload_length !== undefined) {
             upload_data.Metadata.upload_length = file.upload_length;
+        }
 
-        if (file.upload_defer_length !== undefined)
+        if (file.upload_defer_length !== undefined) {
             upload_data.Metadata.upload_defer_length = file.upload_defer_length;
+        }
 
-        if (file.upload_metadata !== undefined)
+        if (file.upload_metadata !== undefined) {
             upload_data.Metadata.upload_metadata = file.upload_metadata;
+        }
 
         if (parsedMetadata.contentType) {
             upload_data.ContentType = parsedMetadata.contentType.decoded;
@@ -258,7 +261,7 @@ class S3Store extends DataStore {
 
             metadata[key] = {
                 encoded: base64_value,
-                decoded: base64_value !== undefined ? Buffer.from(base64_value, 'base64').toString('ascii') : undefined,
+                decoded: base64_value ? Buffer.from(base64_value, 'base64').toString('ascii') : undefined,
             };
 
             return metadata;
@@ -577,7 +580,7 @@ class S3Store extends DataStore {
                 ...this.cache[id].file,
                 size: metadata.file.upload_length,
                 upload_length: metadata.file.upload_length,
-                upload_defer_length: metadata.file.upload_defer_length
+                upload_defer_length: metadata.file.upload_defer_length,
             };
         }
     }