Fix panic when traversing marked map value

ops.go

@@ -217,7 +217,12 @@ func GetAttr(obj cty.Value, attrName string, srcRange *Range) (cty.Value, Diagno
 		}
 
 		idx := cty.StringVal(attrName)
-		if obj.HasIndex(idx).False() {
+
+		// Here we drop marks from HasIndex result, in order to allow basic
+		// traversal of a marked map in the same way we can traverse a marked
+		// object
+		hasIndex, _ := obj.HasIndex(idx).Unmark()
+		if hasIndex.False() {
 			return cty.DynamicVal, Diagnostics{
 				{
 					Severity: DiagError,

ops_test.go

@@ -48,6 +48,15 @@ func TestApplyPath(t *testing.T) {
 			cty.StringVal("hello"),
 			``,
 		},
+		{
+			cty.MapVal(map[string]cty.Value{
+				"a": cty.StringVal("foo").Mark("x"),
+				"b": cty.StringVal("bar").Mark("x"),
+			}).Mark("x"),
+			cty.GetAttrPath("a"),
+			cty.StringVal("foo").Mark("x"),
+			``,
+		},
 		{
 			cty.ListValEmpty(cty.String),
 			(cty.Path)(nil).Index(cty.NumberIntVal(0)),