To summarize:

    FileServices   unregisterFileReader: CornerGripMorph

solves the issue.

The use case in detail

ExternalDropHandler>>handleDroppedItem:event:
http://wiki.squeak.org/squeak/4283

See also thread
'ExternalDropHandler chooseServiceFrom:'

--Hannes

On 3/25/17, H. Hirzel <hannes.hirzel at gmail.com> wrote:
>     FileServices allInstances size
>
> gives
>
>     0
>
> only class methods.
>
> There is
>
>      FileServices initialize.
>
> The #initialize method looks for classes which implement
> #fileReaderServicesForFile:suffix: and asks them to register.
>
>
> The list of classes which implement #fileReaderServicesForFile:suffix:
> is given by
>
>
>     (Smalltalk allClasses select: [:aClass|
> 		(aClass class includesSelector: #fileReaderServicesForFile:suffix:)])
>          sorted: [:a :b | a name < b name]
>
>
> It is
>
> {AnimatedImageMorph . ArchiveViewer . BookMorph . ChangeList .
> ChangeSet . DummyToolWorkingWithFileList . EventRecorderMorph .
> FileContentsBrowser . FileDirectory . FilePackage . FileStream . Form
> . GZipReadStream . GZipWriteStream . InternalTranslator .
> MCVersionReader . MczInstaller . Morph . NaturalLanguageTranslator .
> Object . Preferences . ProjectViewMorph . SARInstaller . ScorePlayer .
> ScorePlayerMorph . TTCFont . TTFontReader}
>
> in Squeak 5.1.
> The CornerGripMorph is _not_ in this list.
>
>
> So
>
>     FileService initialize
>
>
> should do the job.
>
> It has as code
>
> initialize
> 	"FileServices initialize"
> 	
> 	Smalltalk allClassesDo:[:aClass|
> 		(aClass class includesSelector: #fileReaderServicesForFile:suffix:)
> 			ifTrue:[self registerFileReader: aClass]].
>
>
> It does not do it. The double entry of 'Load as morph' still appears.
>
> What #initialize needs to do it to reset the FileReaderRegistry class
> variable
>
> 	FileReaderRegistry := nil.
>
>
> So the updated #initialize method should look like
>
>
> initialize
> 	"FileServices initialize"
> 	
> 	FileReaderRegistry := nil.
>
> 	Smalltalk allClassesDo:[:aClass|
> 		(aClass class includesSelector: #fileReaderServicesForFile:suffix:)
> 			ifTrue:[self registerFileReader: aClass]].
>
>
> Then after
>
>       FileServices initialize
>
> the CornerGripMorph is no longer included.
>
>
> Note: In  spite of this generic direct initialisation mechanism 10
> #initialize methods on the class side directly reference FileServices.
> And MczInstaller has #registerForFileList which references
> FileServices.
>
> So we would need to check if with this change
>
>     	FileReaderRegistry := nil.
>
>
> we still get enough registrations. That is to check each class which
> references FileServices.
>
> On 3/25/17, Edgar De Cleene <edgardec2005 at gmail.com> wrote:
>> You are right.
>> FileServices   unregisterFileReader: CornerGripMorph solves the issue and
>> can’t see any use of having a CornerGripMorph outside of the .image
>>
>>> On Mar 25, 2017, at 08:31, Tobias Pape <Das.Linux at gmx.de> wrote:
>>>
>>> CornerGripMorph
>>
>>
>