Fix crash when resizing double-buffered window smaller than transparent image (STR#3353).

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.4@12117 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

1 files changed, 3 insertions, 0 deletions

diff --git a/src/Fl_Screen_Driver.cxx b/src/Fl_Screen_Driver.cxx
index e9fd4ec73..526f37b1e 100644
--- a/src/Fl_Screen_Driver.cxx
+++ b/src/Fl_Screen_Driver.cxx
@@ -158,6 +158,9 @@ uchar *Fl_Screen_Driver::read_image(uchar *p, int X, int Y, int w, int h, int al
   Fl_RGB_Image *img;
   if (fl_find(fl_window) == 0) { // read from off_screen buffer
     img = read_win_rectangle(p, X, Y, w, h, alpha);
+    if (!img) {
+      return NULL;
+    }
     img->alloc_array = 1;
   } else {
     img = traverse_to_gl_subwindows(Fl_Window::current(), p, X, Y, w, h, alpha, NULL);