Fix bug in VARDESC (#1644)

Author: Stefan Mücke

CHANGES.md

@@ -11,6 +11,7 @@ Features
 
 Bug Fixes
 ---------
+* [#1644](https://github.com/java-native-access/jna/issues/1644): Fix bug in VARDESC causing an illegal memory access - [@stmuecke](https://github.com/stmuecke)
 
 Release 5.15.0
 ==============

contrib/platform/src/com/sun/jna/platform/win32/OaIdl.java

@@ -1398,14 +1398,10 @@ public static class ByReference extends _VARDESC implements
             public VARIANT.ByReference lpvarValue;
 
             public _VARDESC() {
-                setType("lpvarValue");
-                this.read();
             }
 
             public _VARDESC(Pointer pointer) {
                 super(pointer);
-                setType("lpvarValue");
-                this.read();
             }
 
             /**
@@ -1431,9 +1427,15 @@ public VARDESC() {
 
         public VARDESC(Pointer pointer) {
             super(pointer);
-            this._vardesc.setType("lpvarValue");
             this.read();
         }
+
+        @Override
+        public void read() {
+            readField("varkind");
+            this._vardesc.setType(varkind.value == VARKIND.VAR_CONST ? "lpvarValue" : "oInst");
+            super.read();
+        }
     }
 
     @FieldOrder({"tdesc", "_elemdesc"})