Fix a couple of issues with burnIn.

app/qml/BurnInEffect.qml

@@ -25,9 +25,9 @@ Loader {
     }
 
     function restartBlurSource(){
-        prevLastUpdate = 0;
-        lastUpdate = 0;
-        completelyUpdate()
+        prevLastUpdate = timeManager.time;
+        lastUpdate = prevLastUpdate;
+        completelyUpdate();
     }
 
     sourceComponent: Item {
@@ -56,6 +56,10 @@ Loader {
 
             format: ShaderEffectSource.RGBA
 
+            // Enabling smooth with a low burnInQuality causes bad artifacts because the FBO
+            // has different values when it's read back. This lowers the quality, but makes it more consistent.
+            smooth: appSettings.burnInQuality === 1.0
+
             visible: false
 
             Connections {