fix some nullability issues

src/Spectre.Console/Extensions/AnsiConsoleExtensions.Rendering.cs

@@ -34,11 +34,6 @@ namespace Spectre.Console
 
         private static void Render(IAnsiConsole console, RenderContext options, IEnumerable<IRenderable> renderables)
         {
-            if (renderables is null)
-            {
-                return;
-            }
-
             var result = new List<Segment>();
             foreach (var renderable in renderables)
             {

src/Spectre.Console/Extensions/StringExtensions.cs

@@ -23,7 +23,7 @@ namespace Spectre.Console
         /// </summary>
         /// <param name="text">The text to escape.</param>
         /// <returns>A string that is safe to use in markup.</returns>
-        public static string EscapeMarkup(this string text)
+        public static string EscapeMarkup(this string? text)
         {
             if (text == null)
             {
@@ -45,7 +45,7 @@ namespace Spectre.Console
             return Cell.GetCellLength(context, text);
         }
 
-        internal static string Capitalize(this string text, CultureInfo? culture = null)
+        internal static string Capitalize(this string? text, CultureInfo? culture = null)
         {
             if (text == null)
             {

src/Spectre.Console/Extensions/StyleExtensions.cs

@@ -96,11 +96,6 @@ namespace Spectre.Console
                 throw new ArgumentNullException(nameof(style));
             }
 
-            if (source is null)
-            {
-                return style;
-            }
-
             var current = style;
             foreach (var item in source)
             {

src/Spectre.Console/Internal/Ratio.cs

@@ -53,10 +53,7 @@ namespace Spectre.Console.Internal
             var totalRemaining = total;
             var distributedTotal = new List<int>();
 
-            if (minimums == null)
+            minimums ??= ratios.Select(_ => 0).ToList();
-            {
-                minimums = ratios.Select(_ => 0).ToList();
-            }
 
             foreach (var (ratio, minimum) in ratios.Zip(minimums, (a, b) => (a, b)))
             {

src/Spectre.Console/Internal/Text/StyleParser.cs

@@ -72,10 +72,7 @@ namespace Spectre.Console.Internal
                 var decoration = DecorationTable.GetDecoration(part);
                 if (decoration != null)
                 {
-                    if (effectiveDecoration == null)
+                    effectiveDecoration ??= Decoration.None;
-                    {
-                        effectiveDecoration = Decoration.None;
-                    }
 
                     effectiveDecoration |= decoration.Value;
                 }

src/Spectre.Console/Rendering/Segment.cs

@@ -469,7 +469,7 @@ namespace Spectre.Console.Rendering
         /// <param name="segment">The segment to truncate.</param>
         /// <param name="maxWidth">The maximum width that the segment may occupy.</param>
         /// <returns>A new truncated segment, or <c>null</c>.</returns>
-        public static Segment? Truncate(RenderContext context, Segment segment, int maxWidth)
+        public static Segment? Truncate(RenderContext context, Segment? segment, int maxWidth)
         {
             if (context is null)
             {

src/Spectre.Console/Widgets/Progress/ProgressTask.cs

@@ -127,10 +127,7 @@ namespace Spectre.Console
             lock (_lock)
             {
                 var now = DateTime.Now;
-                if (StartTime == null)
+                StartTime ??= now;
-                {
-                    StartTime = now;
-                }
 
                 StopTime = now;
             }