Add feature flag for image editor.

SignalMessaging/ViewControllers/AttachmentApprovalViewController.swift

@@ -1,5 +1,5 @@
 //
-//  Copyright (c) 2018 Open Whisper Systems. All rights reserved.
+//  Copyright (c) 2019 Open Whisper Systems. All rights reserved.
 //
 
 import Foundation
@@ -68,7 +68,8 @@ class SignalAttachmentItem: Hashable {
 
         // Try and make a ImageEditorModel.
         // This will only apply for valid images.
-        if let dataUrl: URL = attachment.dataUrl,
+        if ImageEditorModel.isFeatureEnabled,
+            let dataUrl: URL = attachment.dataUrl,
             dataUrl.isFileURL {
             let path = dataUrl.path
             do {

SignalMessaging/Views/ImageEditor/ImageEditorModel.swift

@@ -1,5 +1,5 @@
 //
-//  Copyright (c) 2018 Open Whisper Systems. All rights reserved.
+//  Copyright (c) 2019 Open Whisper Systems. All rights reserved.
 //
 
 import UIKit
@@ -354,6 +354,12 @@ public protocol ImageEditorModelDelegate: class {
 
 @objc
 public class ImageEditorModel: NSObject {
+
+    @objc
+    public static var isFeatureEnabled: Bool {
+        return _isDebugAssertConfiguration()
+    }
+
     @objc
     public weak var delegate: ImageEditorModelDelegate?