Fix copy()/cloning vectors that have holes (indices w/ null values)

src/Val.cc

@@ -3360,8 +3360,10 @@ ValPtr VectorVal::DoClone(CloneState* state)
 
 	for ( unsigned int i = 0; i < val.vector_val->size(); ++i )
 		{
-		auto v = (*val.vector_val)[i]->Clone(state);
-		vv->val.vector_val->push_back(std::move(v));
+		if ( (*val.vector_val)[i] )
+			vv->val.vector_val->push_back((*val.vector_val)[i]->Clone(state));
+		else
+			vv->val.vector_val->push_back(nullptr);
 		}
 
 	return vv;

testing/btest/Baseline/language.vector/out

@@ -68,3 +68,5 @@ slicing assignment (PASS)
 slicing assignment (PASS)
 slicing assignment grow (PASS)
 slicing assignment shrink (PASS)
+copy of a vector with holes, 11, 11, [0, 1, 2, , , , , , , , 10], [0, 1, 2, , , , , , , , 10]
+copy of a vector with trailing holes, 6, 6, [0, 1, 2, , , ], [0, 1, 2, , , ]

testing/btest/language/vector.zeek

@@ -183,4 +183,15 @@ event zeek_init()
 	test_case( "slicing assignment grow", all_set(v17 == vector(6, 2, 9, 10, 11, 5)) );
 	v17[2:5] = vector(9);
 	test_case( "slicing assignment shrink", all_set(v17 == vector(6, 2, 9, 5)) );
+
+	# Test copying of a vector with holes, as this used to crash.
+	local v18 = vector(0, 1, 2);
+	v18[10] = 10;
+	local v19 = copy(v18);
+	print "copy of a vector with holes", |v18|, |v19|, v18, v19;
+	# Even after removing some elements at the end, any trailing holes should
+	# be preserved after copying;
+	v18[6:] = vector();
+	local v20 = copy(v18);
+	print "copy of a vector with trailing holes", |v18|, |v20|, v18, v20;
 }