AD0001: InvalidOperationException on 2 rules

### Description

The rules `CollectionShouldContainSingleAnalyzer` and `CollectionShouldBeEmptyAnalyzer` throws `InvalidOperationException` with message `This operation does not apply to an empty instance`.

For some weird reason, the stack trace disappear every time I try to expand the issue, this one is the only one which remains:
```csharp
Severity Code Description Project File Line Category Suppression State Tool Detail Description
Warning AD0001 Analyzer 'FluentAssertions.Analyzers.CollectionShouldContainSingleAnalyzer' threw an exception of type 'System.InvalidOperationException' with message 'This operation does not apply to an empty instance.'. SonarScanner.MSBuild.PreProcessor.Tests 1 Compiler Active FluentAssertions.Analyzers Analyzer 'FluentAssertions.Analyzers.CollectionShouldContainSingleAnalyzer' threw the following exception:
'Exception occurred with following context:
Compilation: SonarScanner.MSBuild.PreProcessor.Tests
ISymbol: GetActiveRules_UseParamAsKey (Method)
SyntaxTree: C:\Src\SonarSource\scanner-msbuild\tests\SonarScanner.MSBuild.PreProcessor.Tests\SonarWebServiceTest.cs
SyntaxNode: [TestMethod] public void GetActiveRules_UseParamAsKey ... [MethodDeclarationSyntax]@[12810..14357) (264,8)-(305,9)

System.InvalidOperationException: This operation does not apply to an empty instance.
at System.Collections.Immutable.ImmutableStack`1.Peek()
at FluentAssertions.Analyzers.FluentAssertionsCSharpSyntaxVisitor.VisitElementAccessExpression(ElementAccessExpressionSyntax node)
at Microsoft.CodeAnalysis.CSharp.Syntax.ElementAccessExpressionSyntax.Accept(CSharpSyntaxVisitor visitor)
at Microsoft.CodeAnalysis.CSharp.CSharpSyntaxVisitor.Visit(SyntaxNode node)
at FluentAssertions.Analyzers.FluentAssertionsCSharpSyntaxVisitor.VisitMemberAccessExpression(MemberAccessExpressionSyntax node)
at Microsoft.CodeAnalysis.CSharp.Syntax.MemberAccessExpressionSyntax.Accept(CSharpSyntaxVisitor visitor)
at Microsoft.CodeAnalysis.CSharp.CSharpSyntaxVisitor.Visit(SyntaxNode node)
at FluentAssertions.Analyzers.FluentAssertionsCSharpSyntaxVisitor.VisitMemberAccessExpression(MemberAccessExpressionSyntax node)
at Microsoft.CodeAnalysis.CSharp.Syntax.MemberAccessExpressionSyntax.Accept(CSharpSyntaxVisitor visitor)
at Microsoft.CodeAnalysis.CSharp.CSharpSyntaxVisitor.Visit(SyntaxNode node)
at FluentAssertions.Analyzers.FluentAssertionsCSharpSyntaxVisitor.VisitInvocationExpression(InvocationExpressionSyntax node)
at Microsoft.CodeAnalysis.CSharp.Syntax.InvocationExpressionSyntax.Accept(CSharpSyntaxVisitor visitor)
at Microsoft.CodeAnalysis.CSharp.CSharpSyntaxVisitor.Visit(SyntaxNode node)
at FluentAssertions.Analyzers.FluentAssertionsCSharpSyntaxVisitor.VisitMemberAccessExpression(MemberAccessExpressionSyntax node)
at Microsoft.CodeAnalysis.CSharp.Syntax.MemberAccessExpressionSyntax.Accept(CSharpSyntaxVisitor visitor)
at Microsoft.CodeAnalysis.CSharp.CSharpSyntaxVisitor.Visit(SyntaxNode node)
at FluentAssertions.Analyzers.FluentAssertionsCSharpSyntaxVisitor.VisitInvocationExpression(InvocationExpressionSyntax node)
at Microsoft.CodeAnalysis.CSharp.Syntax.InvocationExpressionSyntax.Accept(CSharpSyntaxVisitor visitor)
at FluentAssertions.Analyzers.FluentAssertionsAnalyzer`1.AnalyzeExpression(ExpressionSyntax expression, SemanticModel semanticModel)
at FluentAssertions.Analyzers.FluentAssertionsAnalyzer`1.AnalyzeCodeBlock(CodeBlockAnalysisContext context)
at Microsoft.CodeAnalysis.Diagnostics.AnalyzerExecutor.<>c__49`2.b__49_0(ValueTuple`2 data)
at Microsoft.CodeAnalysis.Diagnostics.AnalyzerExecutor.ExecuteAndCatchIfThrows_NoLock[TArg](DiagnosticAnalyzer analyzer, Action`1 analyze, TArg argument, Nullable`1 info)
-----
'.

```

### Complete minimal example reproducing the issue

My test project contains quite a lot of tests so it's quite hard to narrow down to the one failing but I hope that the stacktrace will help you understanding the failure.

### Versions

* Fluent Assertions Analyzers v0.11.4
* Fluent Assertions v5.5.3
* Targeting fwk 4.6.1

### Additional Information

Seems to be related to #78

Start at FluentAssertionsCSharpSyntaxVisitor.VisitElementAccessExpression, where the stack trace shows ImmutableStack.Peek() failing, and reproduce it with GetActiveRules_UseParamAsKey in SonarWebServiceTest.cs. Compare the two affected analyzers and add a regression test based on the reported syntax. Done means neither analyzer throws InvalidOperationException or emits AD0001 for this case.

Written by the indexing model from the issue text.