fix: added null check on Android ViewGroup

Author: efstathiosntonas

android/src/main/java/com/lodev09/truesheet/TrueSheetDialog.kt

@@ -70,12 +70,12 @@ class TrueSheetDialog(private val reactContext: ThemedReactContext, private val
   var backgroundColor: Int = Color.WHITE
 
   // 1st child is the content view
-  val contentView: ViewGroup
-    get() = containerView.getChildAt(0) as ViewGroup
+  val contentView: ViewGroup?
+    get() = containerView.getChildAt(0) as? ViewGroup
 
   // 2nd child is the footer view
-  val footerView: ViewGroup
-    get() = containerView.getChildAt(1) as ViewGroup
+  val footerView: ViewGroup?
+    get() = containerView.getChildAt(1) as? ViewGroup
 
   var sizes: Array<Any> = arrayOf("medium", "large")
 
@@ -196,7 +196,7 @@ class TrueSheetDialog(private val reactContext: ThemedReactContext, private val
   }
 
   fun positionFooter() {
-    footerView.apply {
+    footerView?.apply {
       y = (maxScreenHeight - sheetContainerView.top - footerHeight).toFloat()
     }
   }

android/src/main/java/com/lodev09/truesheet/TrueSheetView.kt

@@ -178,8 +178,8 @@ class TrueSheetView(context: Context) :
 
     // Initialize content
     UiThreadUtil.runOnUiThread {
-      setContentHeight(sheetDialog.contentView.height)
-      setFooterHeight(sheetDialog.footerView.height)
+      sheetDialog.contentView?.height?.let { setContentHeight(it) }
+      sheetDialog.footerView?.height?.let { setFooterHeight(it) }
 
       if (initialIndex >= 0) {
         currentSizeIndex = initialIndex