misc: chore: Fix numerous NullReferenceExceptions, InvalidOperationExceptions

src/Ryujinx.UI.Common/App/ApplicationLibrary.cs

@@ -88,11 +88,16 @@ namespace Ryujinx.UI.App.Common
         private static byte[] GetResourceBytes(string resourceName)
         {
             Stream resourceStream = Assembly.GetCallingAssembly().GetManifestResourceStream(resourceName);
-            byte[] resourceByteArray = new byte[resourceStream.Length];
+            if (resourceStream != null)
+            {
+                byte[] resourceByteArray = new byte[resourceStream.Length];
 
-            resourceStream.ReadExactly(resourceByteArray);
+                resourceStream.ReadExactly(resourceByteArray);
 
-            return resourceByteArray;
+                return resourceByteArray;
+            }
+
+            return [];
         }
 
         /// <exception cref="Ryujinx.HLE.Exceptions.InvalidNpdmException">The npdm file doesn't contain valid data.</exception>
@@ -1178,7 +1183,7 @@ namespace Ryujinx.UI.App.Common
                 {
                     string extension = Path.GetExtension(applicationPath)?.ToLower();
 
-                    using FileStream file = new(applicationPath, FileMode.Open, FileAccess.Read);
+                    using FileStream file = new(applicationPath ?? string.Empty, FileMode.Open, FileAccess.Read);
 
                     if (extension == ".nsp" || extension == ".pfs0" || extension == ".xci")
                     {

src/Ryujinx.UI.Common/Helper/FileAssociationHelper.cs

@@ -152,7 +152,7 @@ namespace Ryujinx.UI.Common.Helper
 
                     Logger.Debug?.Print(LogClass.Application, $"Adding type association {ext}");
                     using var openCmd = key.CreateSubKey(@"shell\open\command");
-                    openCmd.SetValue("", $"\"{Environment.ProcessPath}\" \"%1\"");
+                    openCmd?.SetValue("", $"\"{Environment.ProcessPath}\" \"%1\"");
                     Logger.Debug?.Print(LogClass.Application, $"Added type association {ext}");
 
                 }

src/Ryujinx.UI.Common/SystemInfo/WindowsSystemInfo.cs

@@ -36,11 +36,11 @@ namespace Ryujinx.UI.Common.SystemInfo
             {
                 foreach (var cpuObj in cpuObjs)
                 {
-                    return cpuObj["Name"].ToString().Trim();
+                    return cpuObj["Name"].ToString()?.Trim();
                 }
             }
 
-            return Environment.GetEnvironmentVariable("PROCESSOR_IDENTIFIER").Trim();
+            return Environment.GetEnvironmentVariable("PROCESSOR_IDENTIFIER")?.Trim();
         }
 
         [StructLayout(LayoutKind.Sequential)]