[Lazarus] Patch for simple docking.

[Hans-Peter Diettrich]

Mattias Gaertner schrieb:

>> Actual behaviour: 4 Access violations (fix one to get to the next ;) ).
>>
>> Attached small patch fixes the 4 access violations, after which the expected behaviour 
>> occurs. They are all checks to see if a object pointer is not-nil.
> 
> Thanks. Applied.

It were better to fix the issues, instead of hiding where the bugs manifest.

DoDi