Use ArgumentNullException.ThrowIfNull helper method

Did a simple search/replace on the whole repo (except the RSSDP project)
This reduces LOC and should improve performance (methods containing a throw statement don't get inlined)

```
if \((\w+) == null\)
\s+\{
\s+throw new ArgumentNullException\((.*)\);
\s+\}
```

```
ArgumentNullException.ThrowIfNull($1);
```

2 files changed, 4 insertions, 16 deletions

diff --git a/Emby.Server.Implementations/LiveTv/EmbyTV/EmbyTV.cs b/Emby.Server.Implementations/LiveTv/EmbyTV/EmbyTV.cs
index 065309688c..4da6776369 100644
--- a/Emby.Server.Implementations/LiveTv/EmbyTV/EmbyTV.cs
+++ b/Emby.Server.Implementations/LiveTv/EmbyTV/EmbyTV.cs
@@ -1223,10 +1223,7 @@ namespace Emby.Server.Implementations.LiveTv.EmbyTV
 
         private async Task RecordStream(TimerInfo timer, DateTime recordingEndDate, ActiveRecordingInfo activeRecordingInfo)
         {
-            if (timer == null)
-            {
-                throw new ArgumentNullException(nameof(timer));
-            }
+            ArgumentNullException.ThrowIfNull(timer);
 
             LiveTvProgram programInfo = null;
 
@@ -2347,10 +2344,7 @@ namespace Emby.Server.Implementations.LiveTv.EmbyTV
 
         private IEnumerable<TimerInfo> GetTimersForSeries(SeriesTimerInfo seriesTimer)
         {
-            if (seriesTimer == null)
-            {
-                throw new ArgumentNullException(nameof(seriesTimer));
-            }
+            ArgumentNullException.ThrowIfNull(seriesTimer);
 
             var query = new InternalItemsQuery
             {
diff --git a/Emby.Server.Implementations/LiveTv/EmbyTV/ItemDataProvider.cs b/Emby.Server.Implementations/LiveTv/EmbyTV/ItemDataProvider.cs
index 46979bfc57..58b798ce67 100644
--- a/Emby.Server.Implementations/LiveTv/EmbyTV/ItemDataProvider.cs
+++ b/Emby.Server.Implementations/LiveTv/EmbyTV/ItemDataProvider.cs
@@ -84,10 +84,7 @@ namespace Emby.Server.Implementations.LiveTv.EmbyTV
 
         public virtual void Update(T item)
         {
-            if (item == null)
-            {
-                throw new ArgumentNullException(nameof(item));
-            }
+            ArgumentNullException.ThrowIfNull(item);
 
             lock (_fileDataLock)
             {
@@ -107,10 +104,7 @@ namespace Emby.Server.Implementations.LiveTv.EmbyTV
 
         public virtual void Add(T item)
         {
-            if (item == null)
-            {
-                throw new ArgumentNullException(nameof(item));
-            }
+            ArgumentNullException.ThrowIfNull(item);
 
             lock (_fileDataLock)
             {