Fix BEAUti crash for single valued distr inputs (ScalarDistributionInputEditor)

[alexeid]

Problem

Opening the Priors panel in BEAUti with a package that wraps a distribution in another Distribution — e.g. bModelTest's BMTPrior, which has a single ScalarDistribution valued distr input — pops up "Could not add entry for distr" (BEAST2-Dev/bModelTest#10):

java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
	at beastfx.app.inputeditor.ScalarDistributionInputEditor.createComboBox(ScalarDistributionInputEditor.java:627)
	at beastfx.app.inputeditor.ScalarDistributionInputEditor.init(ScalarDistributionInputEditor.java:119)
	at beastfx.app.inputeditor.InputEditorFactory.createInputEditor(InputEditorFactory.java:264)
	at beastfx.app.inputeditor.InputEditorFactory.createInputEditor(InputEditorFactory.java:145)

init() assumed the input is always a list of distributions with a valid item number:

List<?> list = (List<?>) input.get();
PartitionContext context = doc.getContextFor((BEASTInterface) list.get(itemNr));

For a single valued distr input this is reached with the distribution itself as value and itemNr == -1, so it throws. scalarTemplates had already been assigned at that point while templateDomains was still empty, so every editor created afterwards skipped the scalarTemplates == null guard and died on templateDomains.get(k++) — the reported symptom. The combo box change handler already had a branch for non-list inputs, so single valued inputs were clearly meant to be supported.

Fix

• resolve the distribution being edited from either the list entry or the value of the input itself (getDistribution)
• publish the template caches only once they are complete, so a failure can no longer leave them inconsistent
• fall back to the partition context of the object owning the input when the nested distribution has no ID of its own (contextFor)
• register a replacement distribution as output of the object owning the input rather than of the distribution it replaces
• suppress the combo box, rather than throw, when no templates are known, and null check it before adding it to the pane

Test

ScalarDistributionInputEditorTest builds a BeautiDoc from the Standard template and asks InputEditorFactory for an editor for the distr input of a Distribution wrapper twice, which is what BEAUti does when rendering a panel. Without the fix it reproduces both the initial ClassCastException and the IndexOutOfBoundsException from the issue; with the fix it passes.

Full beast-fx suite: 23 run, 0 failures, 0 errors (11 skipped).