Fix null reference and typo in shell feature provider

[Copilot]

Addresses two issues identified in code review of PR #7279:

Null safety in ShellInstalledFeatureProvider.Find()

• Added StartupType != null filter before mapping descriptors, matching the pattern already used in List()
• Prevents NullReferenceException when MapToElsaFeatureDescriptor dereferences StartupType!

// Before: could throw if StartupType is null
var shellFeature = _shellFeatures.FirstOrDefault(sf => MapToFullName(sf) == fullName);

// After: filters null StartupTypes before mapping
var shellFeature = _shellFeatures
    .Where(sf => sf.StartupType != null)
    .FirstOrDefault(sf => MapToFullName(sf) == fullName);

Grammar fix in WorkflowManagementFeature

• Corrected variable descriptor: "all object" → "all objects"

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[greptile-apps]

Greptile Overview

Greptile Summary

This PR makes two focused fixes identified during code review of PR #7279:

• Null safety improvement: Added StartupType != null filter in ShellInstalledFeatureProvider.Find() to match the existing pattern in List(). This prevents a potential NullReferenceException when MapToElsaFeatureDescriptor() dereferences StartupType! on line 48.
• Grammar correction: Fixed typo in WorkflowManagementFeature variable descriptor from "all object" to "all objects"

Both changes are correct and improve code quality. The null safety fix ensures consistency between the two methods and prevents runtime exceptions.

Confidence Score: 5/5

• This PR is safe to merge with no risk
• Both changes are simple, focused fixes with clear benefits: the null check prevents potential runtime exceptions and matches existing patterns, while the typo fix improves documentation quality. No logic changes or side effects.
• No files require special attention

Important Files Changed

Filename	Overview
src/common/Elsa.Features/Services/ShellInstalledFeatureProvider.cs	Added null check for StartupType in Find() method to match the pattern in List(), preventing potential NullReferenceException
src/modules/Elsa.Workflows.Management/ShellFeatures/WorkflowManagementFeature.cs	Fixed grammar in variable descriptor: "all object" → "all objects"