blank lines were ignored in multiline cell labels (replaces patch 1476165)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@39063 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/grid.cpp

@@ -7606,6 +7606,12 @@ void wxGrid::DrawTextRectangle(wxDC& dc,
     {
         const wxString& line = lines[l];
 
+        if ( line.empty() )
+        {
+            *(textOrientation == wxHORIZONTAL ? &y : &x) += dc.GetCharHeight();
+            continue;
+        }
+
         long lineWidth,
              lineHeight;
         dc.GetTextExtent(line, &lineWidth, &lineHeight);