Fix zero blur radius usage for Floating Notifications banners (#244)

Author: mrsnow-git

NotificationBanner/Classes/FloatingNotificationBanner.swift

@@ -133,7 +133,9 @@ private extension FloatingNotificationBanner {
                              cornerRadius: CGFloat = 0,
                              offset: UIOffset = .zero,
                              edgeInsets: UIEdgeInsets? = nil) {
-        guard blurRadius > 0 else { return }
+
+        guard blurRadius >= 0 else { return }
+
         contentView.layer.shadowColor = color.cgColor
         contentView.layer.shadowOpacity = Float(opacity)
         contentView.layer.shadowRadius = blurRadius