json.facets: allBucket:true can cause server errors when combined with refine:true

Another bug that was discovered while testing SOLR-14467...
In some situations, using allBuckets:true in conjunction with refine:true can cause server errors during the "refinement" requests to the individual shards – either NullPointerExceptions from some (nested) SlotAccs when SpecialSlotAcc tries to collect them, or ArrayIndexOutOfBoundsException from CountSlotArrAcc.incrementCount because it's asked to collect to "large" slot# values even though it's been initialized with a size of '1'

NOTE: these problems may be specific to FacetFieldProcessorByArrayDV - i have not yet seen similar failures from FacetFieldProcessorByArrayUIF (those are the only 2 used when doing refinement) but that may just be a fluke of testing.