AUv3: Fall back to view size if AUViewControllerBase preferredContentSize property has a zero size when opening plug-in editor

modules/juce_audio_processors/format_types/juce_AudioUnitPluginFormat.mm

@@ -2411,8 +2411,16 @@ private:
    #if JUCE_SUPPORTS_AUv3
     void requestViewControllerCallback (AUViewControllerBase* controller)
     {
-        auto nsSize = [controller preferredContentSize];
-        auto viewSize = CGSizeMake (nsSize.width, nsSize.height);
+        const auto viewSize = [&controller]
+        {
+            auto size = [controller preferredContentSize];
+
+            if (size.width == 0 || size.height == 0)
+                size = controller.view.frame.size;
+
+            return CGSizeMake (jmax ((CGFloat) 20.0f, size.width),
+                               jmax ((CGFloat) 20.0f, size.height));
+        }();
 
         if (! MessageManager::getInstance()->isThisTheMessageThread())
         {