don't crash in wxGetWindowXXX() if HWND is 0

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@12895 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/utils.cpp

@@ -1381,43 +1381,30 @@ void wxClientDisplayRect(int *x, int *y, int *width, int *height)
 wxString WXDLLEXPORT wxGetWindowText(WXHWND hWnd)
 {
     wxString str;
+
+    if ( hWnd )
+    {
         int len = GetWindowTextLength((HWND)hWnd) + 1;
-    GetWindowText((HWND)hWnd, str.GetWriteBuf(len), len);
+        ::GetWindowText((HWND)hWnd, str.GetWriteBuf(len), len);
         str.UngetWriteBuf();
+    }
 
     return str;
 }
 
 wxString WXDLLEXPORT wxGetWindowClass(WXHWND hWnd)
 {
-#ifdef __WXMICROWIN__
-    // MICROWIN_TODO
-    return wxEmptyString;
-#else
     wxString str;
 
+    // MICROWIN_TODO
+#ifndef __WXMICROWIN__
+    if ( hWnd )
+    {
         int len = 256; // some starting value
 
         for ( ;; )
         {
-        // as we've #undefined GetClassName we must now manually choose the
+            int count = ::GetClassName((HWND)hWnd, str.GetWriteBuf(len), len);
-        // right function to call
-        int count =
-
-        #ifndef __WIN32__
-            GetClassName
-        #else // Win32
-            #ifdef UNICODE
-                GetClassNameW
-            #else // !Unicode
-                #ifdef __TWIN32__
-                    GetClassName
-                #else // !Twin32
-                    GetClassNameA
-                #endif // Twin32/!Twin32
-            #endif // Unicode/ANSI
-        #endif // Win16/32
-                                    ((HWND)hWnd, str.GetWriteBuf(len), len);
 
             str.UngetWriteBuf();
             if ( count == len )
@@ -1431,9 +1418,10 @@ wxString WXDLLEXPORT wxGetWindowClass(WXHWND hWnd)
                 break;
             }
         }
+    }
+#endif // !__WXMICROWIN__
 
     return str;
-#endif
 }
 
 WXWORD WXDLLEXPORT wxGetWindowId(WXHWND hWnd)