Assertion failed when running "Remove unnecessary imports"

on Microsoft.CodeAnalysis.VisualBasic.Emit.UnitTests project (i.e. applying the code fix to the entire project)

```
---------------------------
Assertion Failed: Abort=Quit, Retry=Debug, Ignore=Continue
---------------------------
at Microsoft.CodeAnalysis.FindUsages.DefinitionItemFactory.GetMetadataLocations(ISymbol definition, Solution solution, ProjectId& originatingProjectId) in C:\dotnet-roslyn\src\Features\Core\Portable\FindUsages\DefinitionItemFactory.cs:line 211

at Microsoft.CodeAnalysis.FindUsages.DefinitionItemFactory.ToDefinitionItem(ISymbol definition, ImmutableArray`1 sourceLocations, ImmutableArray`1 classifiedSpans, Solution solution, FindReferencesSearchOptions options, Boolean isPrimary) in C:\dotnet-roslyn\src\Features\Core\Portable\FindUsages\DefinitionItemFactory.cs:line 122

at Microsoft.CodeAnalysis.FindUsages.DefinitionItemFactory.ToNonClassifiedDefinitionItem(ISymbol definition, ImmutableArray`1 locations, Solution solution, FindReferencesSearchOptions options, Boolean isPrimary, Boolean includeHiddenLocations) in C:\dotnet-roslyn\src\Features\Core\Portable\FindUsages\DefinitionItemFactory.cs:line 51

at Microsoft.CodeAnalysis.FindUsages.DefinitionItemFactory.ToNonClassifiedDefinitionItem(ISymbol definition, Solution solution, FindReferencesSearchOptions options, Boolean includeHiddenLocations) in C:\dotnet-roslyn\src\Features\Core\Portable\FindUsages\DefinitionItemFactory.cs:line 39

at Microsoft.CodeAnalysis.FindUsages.DefinitionItemFactory.ToNonClassifiedDefinitionItem(ISymbol definition, Solution solution, Boolean includeHiddenLocations) in C:\dotnet-roslyn\src\Features\Core\Portable\FindUsages\DefinitionItemFactory.cs:line 32

at Microsoft.CodeAnalysis.GoToDefinition.GoToDefinitionFeatureHelpers.d__1.MoveNext() in C:\dotnet-roslyn\src\Features\Core\Portable\GoToDefinition\GoToDefinitionFeatureHelpers.cs:line 94

at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.Start[TStateMachine](TStateMachine& stateMachine)

at Microsoft.CodeAnalysis.GoToDefinition.GoToDefinitionFeatureHelpers.GetDefinitionsAsync(ISymbol symbol, Solution solution, Boolean thirdPartyNavigationAllowed, CancellationToken cancellationToken)

at Microsoft.CodeAnalysis.Navigation.AbstractDefinitionLocationService.<>c__DisplayClass4_0.<g__GetSymbolLocationAsync|2>d.MoveNext() in C:\dotnet-roslyn\src\EditorFeatures\Core\Navigation\AbstractDefinitionLocationService.cs:line 92

at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.Start[TStateMachine](TStateMachine& stateMachine)

at Microsoft.CodeAnalysis.Navigation.AbstractDefinitionLocationService.<>c__DisplayClass4_0.g__GetSymbolLocationAsync|2(Document document, SemanticModel semanticModel)

at Microsoft.CodeAnalysis.Navigation.AbstractDefinitionLocationService.<>c__DisplayClass4_0.<g__GetDefinitionLocationWorkerAsync|0>d.MoveNext() in C:\dotnet-roslyn\src\EditorFeatures\Core\Navigation\AbstractDefinitionLocationService.cs:line 55

at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.Start[TStateMachine](TStateMachine& stateMachine)

at Microsoft.CodeAnalysis.Navigation.AbstractDefinitionLocationService.<>c__DisplayClass4_0.g__GetDefinitionLocationWorkerAsync|0(Document document)

at Microsoft.CodeAnalysis.Navigation.AbstractDefinitionLocationService.d__4.MoveNext() in C:\dotnet-roslyn\src\EditorFeatures\Core\Navigation\AbstractDefinitionLocationService.cs:line 48

at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.Start[TStateMachine](TStateMachine& stateMachine)

at Microsoft.CodeAnalysis.Navigation.AbstractDefinitionLocationService.GetDefinitionLocationAsync(Document document, Int32 position, CancellationToken cancellationToken)

at Microsoft.CodeAnalysis.Editor.NavigableSymbols.NavigableSymbolService.NavigableSymbolSource.d__5.MoveNext() in C:\dotnet-roslyn\src\EditorFeatures\Core\NavigableSymbols\NavigableSymbolService.NavigableSymbolSource.cs:line 44

at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.Start[TStateMachine](TStateMachine& stateMachine)

at Microsoft.CodeAnalysis.Editor.NavigableSymbols.NavigableSymbolService.NavigableSymbolSource.GetNavigableSymbolAsync(SnapshotSpan triggerSpan, CancellationToken cancellationToken)

at Microsoft.VisualStudio.Language.Intellisense.Implementation.GoToDefMouseHandler.<>c__DisplayClass34_1.b__0()

at Microsoft.VisualStudio.Text.Utilities.GuardedOperations.d__41`1.MoveNext()

at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.Start[TStateMachine](TStateMachine& stateMachine)

at Microsoft.VisualStudio.Text.Utilities.GuardedOperations.CallExtensionPointAsync[T](Object errorSource, Func`1 asyncCall, T valueOnThrow)

at Microsoft.VisualStudio.Language.Intellisense.Implementation.GoToDefMouseHandler.d__34.MoveNext()

at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.Start[TStateMachine](TStateMachine& stateMachine)

at Microsoft.VisualStudio.Language.Intellisense.Implementation.GoToDefMouseHandler.QueryNavigableSymbolAsync(IReadOnlyList`1 sources, SnapshotSpan triggerSpan, CancellationToken token)

at Microsoft.VisualStudio.Language.Intellisense.Implementation.GoToDefMouseHandler.d__32.MoveNext()

at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)

at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)

at System.Runtime.CompilerServices.AsyncMethodBuilderCore.MoveNextRunner.Run()

at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()

at System.Threading.ThreadPoolWorkQueue.Dispatch()

---------------------------
Abort Retry Ignore
---------------------------

```

Reproduce the assertion by applying "Remove unnecessary imports" to the Microsoft.CodeAnalysis.VisualBasic.Emit.UnitTests project. Start with Features/Core/Portable/FindUsages/DefinitionItemFactory.cs at line 211, then trace the navigation path through GoToDefinitionFeatureHelpers.cs and AbstractDefinitionLocationService.cs. Done means the code fix completes without triggering the assertion.

Written by the indexing model from the issue text.