Fix Indicator logic, no longer populate when is not loading (such as error)

Author: dreampiggy

SDWebImageSwiftUI/Classes/ImageManager.swift

@@ -34,6 +34,7 @@ class ImageManager : ObservableObject {
         if currentOperation != nil {
             return
         }
+        self.image = nil
         self.isLoading = true
         currentOperation = manager.loadImage(with: url, options: options, context: context, progress: { [weak self] (receivedSize, expectedSize, _) in
             guard let self = self else {

SDWebImageSwiftUI/Classes/Indicator/Indicator.swift

@@ -32,7 +32,7 @@ struct IndicatorViewModifier<T> : ViewModifier where T : View {
     let indicatorView: T
 
     func body(content: Content) -> some View {
-        if (imageManager.image != nil) && !imageManager.isLoading {
+        if !imageManager.isLoading {
             // Disable Indiactor
             return AnyView(content)
         } else {