Fix #3702: Don't rewrite GetValueOrDefault() to == true in ?. chains

Turning bool?.GetValueOrDefault() into `== true` ends an enclosing
null-conditional chain, so `c?.Flag.GetValueOrDefault()` became
`(c?.Flag == true)` of type bool instead of bool?. A following `?? false`
then fails to compile (CS0019), and a following `.ToString()` yields
"False" instead of null when c is null. Keep the call when its target is
part of a ?. chain.

ICSharpCode.Decompiler/CSharp/CallBuilder.cs

@@ -26,6 +26,7 @@ using System.Text;
 
 using ICSharpCode.Decompiler.CSharp.Resolver;
 using ICSharpCode.Decompiler.CSharp.Syntax;
+using ICSharpCode.Decompiler.CSharp.Transforms;
 using ICSharpCode.Decompiler.IL;
 using ICSharpCode.Decompiler.IL.Transforms;
 using ICSharpCode.Decompiler.Semantics;
@@ -594,7 +595,8 @@ namespace ICSharpCode.Decompiler.CSharp
 			if (settings.LiftNullables && method.Name == "GetValueOrDefault"
 				&& method.DeclaringType.IsKnownType(KnownTypeCode.NullableOfT)
 				&& method.DeclaringType.TypeArguments[0].IsKnownType(KnownTypeCode.Boolean)
-				&& argumentList.Length == 0)
+				&& argumentList.Length == 0
+				&& !IntroduceQueryExpressions.IsNullConditional(target))
 			{
 				argumentList.CheckNoNamedOrOptionalArguments();
 				return new BinaryOperatorExpression(

ICSharpCode.Decompiler/CSharp/Transforms/IntroduceQueryExpressions.cs

@@ -380,7 +380,7 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 			}
 		}
 
-		bool IsNullConditional(Expression target) => target switch {
+		internal static bool IsNullConditional(Expression target) => target switch {
 			UnaryOperatorExpression { Operator: UnaryOperatorType.NullConditional } => true,
 			MemberReferenceExpression member => IsNullConditional(member.Target),
 			InvocationExpression invocation => IsNullConditional(invocation.Target),