fix potential bug in sorting of node-sequences

Author: kingaa

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: phylopomp
 Type: Package
 Title: Phylodynamic Inference for POMP Models
-Version: 0.15.2.0
+Version: 0.15.2.1
 Date: 2026-01-29
 Authors@R: c(person(given=c("Aaron","A."),family="King",role=c("aut","cre"),email="kingaa@umich.edu",comment=c(ORCID="0000-0001-6159-3207")),
 	  person(given=c("Qianying"),family="Lin",role=c("aut"),comment=c(ORCID="0000-0001-8620-9910"))

src/nodeseq.h

@@ -97,7 +97,8 @@ class nodeseq_t : public std::list<node_t*> {
   static bool compare (node_t* p, node_t* q) {
     return (p->slate < q->slate) ||
       ((p->slate == q->slate) &&
-       ((p==q->green_ball()->holder()) || (p->uniq < q->uniq)));
+       ((p==q->green_ball()->holder()) ||
+	((q!=p->green_ball()->holder()) && (p->uniq < q->uniq))));
   };
 
 public: