Add some null checks (#1033)

Co-authored-by: Brandon Minnick <13558917+brminnick@users.noreply.github.com>
Co-authored-by: Javier Suárez <javiersuarezruiz@hotmail.com>
Co-authored-by: Gerald Versluis <gerald.versluis@microsoft.com>

src/CommunityToolkit/Xamarin.CommunityToolkit/Views/TabView/TabView.shared.cs

@@ -958,11 +958,27 @@ void UpdateIsTabStripVisible(bool isTabStripVisible)
 
 		void UpdateTabContentHeight(double tabContentHeight) => contentContainer.HeightRequest = tabContentHeight;
 
-		void UpdateTabIndicatorColor(Color tabIndicatorColor) => tabStripIndicator.BackgroundColor = tabIndicatorColor;
+		void UpdateTabIndicatorColor(Color tabIndicatorColor)
+		{
+			if (tabStripIndicator != null)
+				tabStripIndicator.BackgroundColor = tabIndicatorColor;
+		}
 
-		void UpdateTabIndicatorHeight(double tabIndicatorHeight) => tabStripIndicator.HeightRequest = tabIndicatorHeight;
+		void UpdateTabIndicatorHeight(double tabIndicatorHeight)
+		{
+			if (tabStripIndicator != null)
+			{
+				tabStripIndicator.HeightRequest = tabIndicatorHeight;
+			}
+		}
 
-		void UpdateTabIndicatorWidth(double tabIndicatorWidth) => tabStripIndicator.WidthRequest = tabIndicatorWidth;
+		void UpdateTabIndicatorWidth(double tabIndicatorWidth)
+		{
+			if (tabStripIndicator != null)
+			{
+				tabStripIndicator.WidthRequest = tabIndicatorWidth;
+			}
+		}
 
 		void UpdateTabIndicatorView(View tabIndicatorView)
 		{
@@ -991,9 +1007,21 @@ void UpdateTabIndicatorPlacement(TabIndicatorPlacement tabIndicatorPlacement)
 			UpdateTabIndicatorMargin();
 		}
 
-		void UpdateIsSwipeEnabled(bool isSwipeEnabled) => contentContainer.IsSwipeEnabled = isSwipeEnabled;
+		void UpdateIsSwipeEnabled(bool isSwipeEnabled)
+		{
+			if (contentContainer != null)
+			{
+				contentContainer.IsSwipeEnabled = isSwipeEnabled;
+			}
+		}
 
-		void UpdateIsTabTransitionEnabled(bool isTabTransitionEnabled) => contentContainer.IsScrollAnimated = isTabTransitionEnabled;
+		void UpdateIsTabTransitionEnabled(bool isTabTransitionEnabled)
+		{
+			if (contentContainer != null)
+			{
+				contentContainer.IsScrollAnimated = isTabTransitionEnabled;
+			}
+		}
 
 		void UpdateTabIndicatorPosition(int tabViewItemIndex)
 		{