Make kotlin 1.3.31 happy with EasterEgg

Don't know what the deal is, but I had to make these changes to make a
newer kotlin compiler happy

Test: builds
Change-Id: Id5a85c787876248e610cc668f54e7bd40629d4e0

packages/EasterEgg/src/com/android/egg/paint/BrushPropertyDrawable.kt

@@ -62,8 +62,8 @@ class BrushPropertyDrawable : Drawable {
         return _size
     }
 
-    override fun draw(c: Canvas?) {
-        c?.let {
+    override fun draw(c: Canvas) {
+        c.let {
             val w = bounds.width().toFloat()
             val h = bounds.height().toFloat()
             val inset = _size / 12 // 2dp in a 24x24 icon

packages/EasterEgg/src/com/android/egg/paint/Painting.kt

@@ -337,11 +337,11 @@ public class Painting : View, SpotFilter.Plotter {
                             bits.width.toFloat() / oldBits.height,
                             bits.height.toFloat() / oldBits.width)
                 }
-                c.matrix = matrix
+                c.setMatrix(matrix)
             }
             // paint the old artwork atop the new
             c.drawBitmap(oldBits, 0f, 0f, _drawPaint)
-            c.matrix = Matrix()
+            c.setMatrix(Matrix())
         } else {
             c.drawColor(paperColor)
         }