fix json imagemeter

iOSClient/Imagemeter/IMImagemeter.swift

@@ -33,7 +33,7 @@ class IMImagemeterCodable: NSObject {
         }
         
         struct color: Codable {
-            let rgba: [Int]
+            let rgba: [Int]?
         }
         
         struct end_pt: Codable {
@@ -114,7 +114,7 @@ class IMImagemeterCodable: NSObject {
         struct elements: Codable {
             let id: Int
             let class_: String
-            let center: coordinates
+            let center: coordinates?
             let width: CGFloat?
             let arrows: [end_pt]?
             let text: String?

iOSClient/Viewer/NCViewerImagemeter.swift

@@ -124,7 +124,7 @@ class NCViewerImagemeter: NSObject {
                     continue
                 }
                 
-                let center = IMImagemeterCodable.sharedInstance.convertCoordinate(x: element.center.x, y: element.center.y, width: imagemeterView.bounds.width, height: imagemeterView.imageHeightConstraint.constant)
+                let center = IMImagemeterCodable.sharedInstance.convertCoordinate(x: element.center?.x ?? 0, y: element.center?.y ?? 0, width: imagemeterView.bounds.width, height: imagemeterView.imageHeightConstraint.constant)
                 
                 let button = UIButton()
                 button.frame = CGRect(x: center.x - dimButton/2, y: center.y - dimButton/2, width: dimButton, height: dimButton)