Fix DEBUG_VERBOSE print of uninitialized Result::endRemaining

Point writes are recorded with the 2-argument interleaved_insert::Result
constructor, which left endRemaining (and nextRangeWrite) indeterminate.
The Phase 2 debug print then unconditionally printed endRemaining, so any
DEBUG_VERBOSE && !NDEBUG build read an indeterminate span and, with stack
garbage from a previous call, dereferenced a freed pointer. Initialize the
range-only members in both constructors, and only print the end search
path/spans for range writes.

ConflictSet.cpp

@@ -3904,11 +3904,12 @@ struct Result {
   Result() = default;
   Result(Node *insertionPoint, TrivialSpan remaining)
       : insertionPoint(insertionPoint), remaining(remaining),
-        endInsertionPoint(nullptr) {}
+        endInsertionPoint(nullptr), endRemaining{}, nextRangeWrite(nullptr) {}
   Result(Node *insertionPoint, TrivialSpan remaining, Node *endInsertionPoint,
          TrivialSpan endRemaining)
       : insertionPoint(insertionPoint), remaining(remaining),
-        endInsertionPoint(endInsertionPoint), endRemaining(endRemaining) {}
+        endInsertionPoint(endInsertionPoint), endRemaining(endRemaining),
+        nextRangeWrite(nullptr) {}
 
   Node *insertionPoint;
   TrivialSpan remaining;
@@ -4979,9 +4980,11 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
         fprintf(stderr, "search path: %s, begin: %s\n",
                 getSearchPathPrintable(b).c_str(),
                 printable(context.results[i].remaining).c_str());
-        fprintf(stderr, "search path: %s, end: %s\n",
-                getSearchPathPrintable(e).c_str(),
-                printable(context.results[i].endRemaining).c_str());
+        if (e != nullptr) {
+          fprintf(stderr, "search path: %s, end: %s\n",
+                  getSearchPathPrintable(e).c_str(),
+                  printable(context.results[i].endRemaining).c_str());
+        }
       }
 #endif