OverlappingAMR: crash when using Convert To Multiblock

ParaView segfault when we use the Convert To Multiblock filter on an overlappingAMR.

tested with master and the binary release 5.12.0.

To Reproduce

• create an AMRGaussianPulseSource
• apply the Convert to Multiblock
• paraview segfault

trace on master

(  15.927s) [paraview        ]  vtkDataObjectTree.cxx:442    ERR| vtkMultiBlockDataSet (0x55d10fc87f80): Invalid iterator location.
[jafar:339091] *** Process received signal ***                                                                                     
[jafar:339091] Signal: Segmentation fault (11)                                                                                     
[jafar:339091] Signal code: Address not mapped (1)                                                                                 
[jafar:339091] Failing at address: 0x50                                                                                            
[jafar:339091] [ 0] /lib/x86_64-linux-gnu/libpthread.so.0(+0x14420)[0x7f2be2d51420]                                                
[jafar:339091] [ 1] /home/jafar/dev/paraview/build/bin/../lib/libvtkCommonCore-pv5.12.so.1(_ZN14vtkInformation4CopyEPS_i+0x22)[0x7f2be4423be2]                                                                                                                        
[jafar:339091] [ 2] /home/jafar/dev/paraview/build/bin/../lib/libvtkFiltersCore-pv5.12.so.1(_ZN29vtkConvertToMultiBlockDataSet7ExecuteEP13vtkDataObjectP20vtkMultiBlockDataSet+0xbb)[0x7f2be62c763b]                                                                  
[jafar:339091] [ 3] /home/jafar/dev/paraview/build/bin/../lib/libvtkFiltersCore-pv5.12.so.1(_ZN29vtkConvertToMultiBlockDataSet11RequestDataEP14vtkInformationPP20vtkInformationVectorS3_+0x34)[0x7f2be62c7774]                                                        
[jafar:339091] [ 4] /home/jafar/dev/paraview/build/bin/../lib/libvtkFiltersParallel-pv5.12.so.1(_ZN30vtkPConvertToMultiBlockDataSet11RequestDataEP14vtkInformationPP20vtkInformationVectorS3_+0xa1)[0x7f2bdd04cb81]                                                   
[jafar:339091] [ 5] /home/jafar/dev/paraview/build/bin/../lib/libvtkCommonExecutionModel-pv5.12.so.1(_ZN12vtkExecutive13CallAlgorithmEP14vtkInformationiPP20vtkInformationVectorS3_+0x5d)[0x7f2be5f7cfad]                                                             
[jafar:339091] [ 6] /home/jafar/dev/paraview/build/bin/../lib/libvtkCommonExecutionModel-pv5.12.so.1(_ZN23vtkDemandDrivenPipeline11ExecuteDataEP14vtkInformationPP20vtkInformationVectorS3_+0x3d)[0x7f2be5f7324d]                                                     
[jafar:339091] [ 7] /home/jafar/dev/paraview/build/bin/../lib/libvtkCommonExecutionModel-pv5.12.so.1(_ZN24vtkCompositeDataPipeline1
1ExecuteDataEP14vtkInformationPP20vtkInformationVectorS3_+0x81)[0x7f2be5f6fac1]                                                    
[jafar:339091] [ 8] /home/jafar/dev/paraview/build/bin/../lib/libvtkCommonExecutionModel-pv5.12.so.1(_ZN23vtkDemandDrivenPipeline14ProcessRequestEP14vtkInformationPP20vtkInformationVectorS3_+0x30d)[0x7f2be5f7654d]                                                 
[jafar:339091] [ 9] /home/jafar/dev/paraview/build/bin/../lib/libvtkCommonExecutionModel-pv5.12.so.1(_ZN32vtkStreamingDemandDrivenPipeline14ProcessRequestEP14vtkInformationPP20vtkInformationVectorS3_+0x549)[0x7f2be5fbc259]                                        
[jafar:339091] [10] /home/jafar/dev/paraview/build/bin/../lib/libvtkCommonExecutionModel-pv5.12.so.1(_ZN24vtkCompositeDataPipeline15ForwardUpstreamEP14vtkInformation+0x182)[0x7f2be5f6e902]                                                                          
[jafar:339091] [11] /home/jafar/dev/paraview/build/bin/../lib/libvtkCommonExecutionModel-pv5.12.so.1(_ZN23vtkDemandDrivenPipeline14ProcessRequestEP14vtkInformationPP20vtkInformationVectorS3_+0x13a)[0x7f2be5f7637a]