Null-safeguard RedumpLib conversions

CHANGELIST.md

@@ -10,6 +10,7 @@
 - Update to Aaru v5.3.0-rc2
 - Add .NET 5.0 as build target
 - Remove .NET Core 3.1 and .NET 5.0 from AppVeyor build artifacts
+- Null-safeguard RedumpLib conversions
 
 ### 2.1 (2021-07-22)
 - Enum, no more

RedumpLib/Data/Extensions.cs

@@ -800,7 +800,7 @@ namespace RedumpLib.Data
         /// <returns>Category represented by the string, if possible</returns>
         public static DiscCategory? ToDiscCategory(string category)
         {
-            switch (category.ToLowerInvariant())
+            switch (category?.ToLowerInvariant())
             {
                 case "games":
                     return DiscCategory.Games;
@@ -849,7 +849,7 @@ namespace RedumpLib.Data
         /// <returns>DiscType represented by the string, if possible</returns>
         public static DiscType? ToDiscType(string discType)
         {
-            switch (discType.ToLowerInvariant())
+            switch (discType?.ToLowerInvariant())
             {
                 case "bd25":
                 case "bd-25":
@@ -1316,7 +1316,7 @@ namespace RedumpLib.Data
         /// <returns>RedumpSystem represented by the string, if possible</returns>
         public static RedumpSystem? ToRedumpSystem(string system)
         {
-            switch (system.ToLowerInvariant())
+            switch (system?.ToLowerInvariant())
             {
                 #region BIOS Sets
 
@@ -2158,7 +2158,7 @@ namespace RedumpLib.Data
         /// <returns>YesNo represented by the string, if possible</returns>
         public static YesNo? ToYesNo(string yesno)
         {
-            switch (yesno.ToLowerInvariant())
+            switch (yesno?.ToLowerInvariant())
             {
                 case "no":
                     return YesNo.No;