kernel: Trying to lock an empty global memory block gives an ERROR_DISCARDED.

dlls/kernel/heap.c

@@ -413,9 +413,11 @@ LPVOID WINAPI GlobalLock(
         pintern = HANDLE_TO_INTERN(hmem);
         if (pintern->Magic == MAGIC_GLOBAL_USED)
         {
-            if (pintern->LockCount < GLOBAL_LOCK_MAX)
-                pintern->LockCount++;
             palloc = pintern->Pointer;
+            if (!pintern->Pointer)
+                SetLastError(ERROR_DISCARDED);
+            else if (pintern->LockCount < GLOBAL_LOCK_MAX)
+                    pintern->LockCount++;
         }
         else
         {

dlls/kernel/tests/heap.c

@@ -102,4 +102,12 @@ START_TEST(heap)
     gbl = LocalReAlloc(0, 10, LMEM_MOVEABLE);
     ok(gbl == NULL, "local realloc allocated memory\n");
 
+    /* trying to lock empty memory should give an error */
+    gbl = GlobalAlloc(GMEM_MOVEABLE|GMEM_ZEROINIT,0);
+    ok(gbl != NULL, "returned NULL\n");
+    SetLastError(0xdeadbeef);
+    mem = GlobalLock(gbl);
+    ok( GetLastError() == ERROR_DISCARDED, "should return an error\n");
+    ok( mem == NULL, "should return NULL\n");
+    GlobalFree(gbl);
 }