Fix Android Studio OSC layout preview (again)

The layout preview/editor doesn't instantiate an Application instance, therefore accessing `displayMetrics` from the app context would lead to a crash, and the view being mocked in the preview.
Additionally a default grid value is defined for `AlignmentGridView` to avoid a crash because of an invalid iteration step in the drawing loop.

app/src/main/java/emu/skyline/input/onscreen/OnScreenEditInfo.kt

@@ -5,8 +5,8 @@
 
 package emu.skyline.input.onscreen
 
+import android.content.res.Resources
 import android.util.TypedValue
-import emu.skyline.SkylineApplication
 
 enum class EditMode {
     None,
@@ -39,10 +39,9 @@ class OnScreenEditInfo {
     val isEditing get() = editMode != EditMode.None
 
     companion object {
-
         /**
          * The size of the grid, calculated from the value of 8dp
          */
-        val GridSize = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 8f, SkylineApplication.context.resources.displayMetrics).toInt()
+        var GridSize = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 8f, Resources.getSystem().displayMetrics).toInt()
     }
 }

app/src/main/java/emu/skyline/views/AlignmentGridView.kt

@@ -16,7 +16,7 @@ import android.view.View
  * A view that draws a grid, used for aligning on-screen controller buttons
  */
 class AlignmentGridView @JvmOverloads constructor(context : Context, attrs : AttributeSet? = null, defStyleAttr : Int = 0) : View(context, attrs, defStyleAttr) {
-    var gridSize = 0
+    var gridSize = 16
         set(value) {
             field = value
             invalidate()