fixes an issue where unwind doesn't work on null map of outNull

conformance/tests/ot_null.py

@@ -33,9 +33,19 @@ def test_returnNil(man):
         #print(i)
         count_1 += 1
 
-    return errors    
+    return errors
+
+def test_returnNilUnwind(man):
+    errors = []
 
+    G = man.setGraph("swapi")
+
+    # outNull generates null maps that must be skipped in the unwind step. Was causing segfault before.
+    for i in G.query().V().outNull("species").unwind('eye_colors'):
+        if i['data']['eye_colors'] is not None and not isinstance(i['data']['eye_colors'], str):
+            errors.append("expecting i['eye_colors'] to be string after unwind but got %s instead" % i['eye_colors'])
 
+    return errors
 def test_hasLabelOut(man):
     errors = []
 

engine/core/processors.go

@@ -564,16 +564,19 @@ func (r *Unwind) Process(ctx context.Context, man gdbi.Manager, in gdbi.InPipe,
 				}
 			} else {
 				cur := t.GetCurrent()
-				o := gdbi.DataElement{
-					ID:    cur.Get().ID,
-					Label: cur.Get().Label,
-					From:  cur.Get().From,
-					To:    cur.Get().To,
-					Data:  copy.DeepCopy(cur.Get().Data).(map[string]interface{}), Loaded: true,
+				// if outnull returns null cur can be empty
+				if cur.Get() != nil {
+					o := gdbi.DataElement{
+						ID:    cur.Get().ID,
+						Label: cur.Get().Label,
+						From:  cur.Get().From,
+						To:    cur.Get().To,
+						Data:  copy.DeepCopy(cur.Get().Data).(map[string]interface{}), Loaded: true,
+					}
+					n := t.AddCurrent(&o)
+					gdbi.TravelerSetValue(n, r.Field, nil)
+					out <- n
 				}
-				n := t.AddCurrent(&o)
-				gdbi.TravelerSetValue(n, r.Field, nil)
-				out <- n
 			}
 		}
 	}()