Fix UIVisualEffectView

[KingOfBrian]

Code generation is not correct. There's also some curious double-nesting in xib files when created fresh, ie:

        <visualEffectView opaque="NO" contentMode="scaleToFill" id="JqZ-8z-GcL">
            <rect key="frame" x="0.0" y="0.0" width="240" height="128"/>
            <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMaxY="YES"/>
            <view key="contentView" opaque="NO" clipsSubviews="YES" multipleTouchEnabled="YES" contentMode="center" id="qar-2Q-g4b">
                <frame key="frameInset"/>
                <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                <subviews>
                    <visualEffectView opaque="NO" contentMode="scaleToFill" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="oio-Xx-v59">
                        <frame key="frameInset"/>
                        <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                        <view key="contentView" opaque="NO" clipsSubviews="YES" multipleTouchEnabled="YES" contentMode="center" ambiguous="YES" id="AIi-sS-Vsr">
                            <frame key="frameInset"/>
                            <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                        </view>
                        <vibrancyEffect>
                            <blurEffect style="light"/>
                        </vibrancyEffect>
                    </visualEffectView>
                </subviews>
            </view>
            <vibrancyEffect>
                <blurEffect style="light"/>
            </vibrancyEffect>
            <point key="canvasLocation" x="326" y="485"/>
        </visualEffectView>

Wonder if the view hierarchy that's created is as strange as the XML looks.