Weight summarisation by atlas not available for multimodal data without per-region kernels

[mouraomiranda]

When a user computes kernels from multiple modalities but does not use an atlas (or other feature grouping) to compute one kernel per region or group, the option to compute one weight per region or grouping in the weight visualisation window will not work correctly.

This option is only supported in the following two cases:

• The user has used a single kernel or non-kernel approach and selected an atlas to summarise the weights a posteriori.
• The user has computed one kernel per region or grouping using an atlas.

Users computing multimodal kernels without per-region grouping attempting to use this option will see an error in the Display Weights windows.