Report NewHighsNewLows as not ready while no asset is tracked

Indicators/NewHighsNewLows.cs

@@ -233,9 +233,12 @@ private bool HasMissingCurrentPeriodValue()
 
         private bool HasSufficientPreviousDataForComputation()
         {
-            return _trackedAssets.All(asset =>
-                asset.RollingPreviousHigh.IsReady
-                && asset.RollingPreviousLow.IsReady);
+            // All() holds over an empty set, so without this the indicator reports itself
+            // ready before any asset is tracked
+            return _trackedAssets.Any()
+                && _trackedAssets.All(asset =>
+                    asset.RollingPreviousHigh.IsReady
+                    && asset.RollingPreviousLow.IsReady);
         }
 
         private void UpdatePreviousValues(TrackedAsset asset, IBaseDataBar bar)

Tests/Indicators/NewHighsNewLowsTestsBase.cs

@@ -162,5 +162,24 @@ public override void AcceptsVolumeRenkoBarsAsInput()
                 ibmRenkoConsolidator.Dispose();
             }
         }
+
+        [Test]
+        public void IsNotReadyWithoutTrackedAssets()
+        {
+            var indicator = CreateNewHighsNewLowsIndicator();
+
+            Assert.IsFalse(indicator.IsReady);
+        }
+
+        [Test]
+        public void IsNotReadyOnceTheLastTrackedAssetIsRemoved()
+        {
+            var indicator = CreateNewHighsNewLowsIndicator();
+            indicator.Add(Symbols.AAPL);
+            indicator.Remove(Symbols.AAPL);
+
+            Assert.IsFalse(indicator.IsReady);
+        }
+
     }
 }