windowscodecs: Fix *_CopyPixels functions to properly handle a NULL rectangle

[Vincent Povirk]

+1

+        if (!prc)
+        {
+            UINT width, height;
+            hr = IWICBitmapSource_GetSize(This->source, &width, &height);
+            if (FAILED(hr)) return hr;
+            rc.X = 0;
+            rc.Y = 0;
+            rc.Width = width;
+            rc.Height = height;
+            prc = &rc;
+        }

Any reason you didn't use this approach in the other functions?