[Fix] Possible null reference. (#4585)

Fix possible null reference.

MediaBrowser.Common/Plugins/LocalPlugin.cs

@@ -1,11 +1,11 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Globalization;
 
 namespace MediaBrowser.Common.Plugins
 {
     /// <summary>
-    /// Local plugin struct.
+    /// Local plugin class.
     /// </summary>
     public class LocalPlugin : IEquatable<LocalPlugin>
     {
@@ -106,6 +106,12 @@ namespace MediaBrowser.Common.Plugins
         /// <inheritdoc />
         public bool Equals(LocalPlugin other)
         {
+            // Do not use == or != for comparison as this class overrides the operators.
+            if (object.ReferenceEquals(other, null))
+            {
+                return false;
+            }
+
             return Name.Equals(other.Name, StringComparison.OrdinalIgnoreCase)
                    && Id.Equals(other.Id);
         }