fix: Rethrow exception on RaiseAndSetIfChanged (#2035)

Author: RLittlesII

src/ReactiveUI.Tests/ReactiveObject/ReactiveObjectTests.cs

@@ -7,6 +7,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Reactive.Concurrency;
+using System.Reactive.Linq;
 using DynamicData;
 using Xunit;
 
@@ -196,5 +197,18 @@ public void ReactiveObjectSmokeTest()
             output.AssertAreEqual(output_changing);
             results.AssertAreEqual(output);
         }
+
+        [Fact]
+        public void ReactiveObjectShouldRethrowException()
+        {
+            var fixture = new TestFixture();
+            var observable = fixture.WhenAnyValue(x => x.IsOnlyOneWord).Skip(1);
+            observable.Subscribe(x => throw new Exception("This is a test."));
+
+            var result = Record.Exception(() => fixture.IsOnlyOneWord = "Two Words");
+
+            Assert.IsType<Exception>(result);
+            Assert.Equal("This is a test.", result.Message);
+        }
     }
 }

src/ReactiveUI/ReactiveObject/IReactiveObjectExtensions.cs

@@ -391,7 +391,10 @@ internal void NotifyObservable<T>(TSender rxObj, T item, ISubject<T> subject)
                     if (_thrownExceptions.IsValueCreated)
                     {
                         _thrownExceptions.Value.OnNext(ex);
+                        return;
                     }
+
+                    throw;
                 }
             }
         }