Substitute null name properties with empty string in default constructor

Author: mdh1418

src/libraries/System.Private.CoreLib/src/System/TimeZoneInfo.Win32.cs

@@ -91,18 +91,24 @@ public AdjustmentRule[] GetAdjustmentRules()
         private static string? PopulateDisplayName()
         {
             // Keep window's implementation to populate via constructor
+            // This should not be reached
+            Debug.Assert(false);
             return null;
         }
 
         private static string? PopulateStandardDisplayName()
         {
             // Keep window's implementation to populate via constructor
+            // This should not be reached
+            Debug.Assert(false);
             return null;
         }
 
         private static string? PopulateDaylightDisplayName()
         {
             // Keep window's implementation to populate via constructor
+            // This should not be reached
+            Debug.Assert(false);
             return null;
         }
 
@@ -918,9 +924,9 @@ private static TimeZoneInfoResult TryGetTimeZoneFromLocalMachine(string id, out
                     value = new TimeZoneInfo(
                         id,
                         new TimeSpan(0, -(defaultTimeZoneInformation.Bias), 0),
-                        displayName,
-                        standardName,
-                        daylightName,
+                        displayName ?? string.Empty,
+                        standardName ?? string.Empty,
+                        daylightName ?? string.Empty,
                         adjustmentRules,
                         disableDaylightSavingTime: false);
 

src/libraries/System.Private.CoreLib/src/System/TimeZoneInfo.cs

@@ -989,9 +989,9 @@ private TimeZoneInfo(
 
             _id = id;
             _baseUtcOffset = baseUtcOffset;
-            _displayName = displayName;
-            _standardDisplayName = standardDisplayName;
-            _daylightDisplayName = disableDaylightSavingTime ? null : daylightDisplayName;
+            _displayName = displayName ?? string.Empty;
+            _standardDisplayName = standardDisplayName ?? string.Empty;
+            _daylightDisplayName = disableDaylightSavingTime ? string.Empty : daylightDisplayName ?? string.Empty;
             _supportsDaylightSavingTime = adjustmentRulesSupportDst && !disableDaylightSavingTime;
             _adjustmentRules = adjustmentRules;
 
@@ -1012,9 +1012,9 @@ public static TimeZoneInfo CreateCustomTimeZone(
             return new TimeZoneInfo(
                 id,
                 baseUtcOffset,
-                displayName ?? string.Empty,
-                standardDisplayName ?? string.Empty,
-                standardDisplayName ?? string.Empty,
+                displayName,
+                standardDisplayName,
+                standardDisplayName,
                 adjustmentRules: null,
                 disableDaylightSavingTime: false,
                 hasIanaId);
@@ -1034,9 +1034,9 @@ public static TimeZoneInfo CreateCustomTimeZone(
             return CreateCustomTimeZone(
                 id,
                 baseUtcOffset,
-                displayName ?? string.Empty,
-                standardDisplayName ?? string.Empty,
-                daylightDisplayName ?? string.Empty,
+                displayName,
+                standardDisplayName,
+                daylightDisplayName,
                 adjustmentRules,
                 disableDaylightSavingTime: false);
         }
@@ -1063,9 +1063,9 @@ public static TimeZoneInfo CreateCustomTimeZone(
             return new TimeZoneInfo(
                 id,
                 baseUtcOffset,
-                displayName ?? string.Empty,
-                standardDisplayName ?? string.Empty,
-                daylightDisplayName ?? string.Empty,
+                displayName,
+                standardDisplayName,
+                daylightDisplayName,
                 adjustmentRules,
                 disableDaylightSavingTime,
                 hasIanaId);