Mac OS: handle possible NULL return after screen capture attempt.

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.3@10078 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

1 files changed, 7 insertions, 5 deletions

diff --git a/src/fl_scroll_area.cxx b/src/fl_scroll_area.cxx
index 7531f3d90..a8cba57c4 100644
--- a/src/fl_scroll_area.cxx
+++ b/src/fl_scroll_area.cxx
@@ -143,11 +143,13 @@ void fl_scroll(int X, int Y, int W, int H, int dx, int dy,
 
 #elif defined(__APPLE_QUARTZ__)
   CGImageRef img = Fl_X::CGImage_from_window_rect(Fl_Window::current(), src_x, src_y, src_w, src_h);
-  CGRect rect = { { dest_x, dest_y }, { src_w, src_h } };
-  Fl_X::q_begin_image(rect, 0, 0, src_w, src_h);
-  CGContextDrawImage(fl_gc, rect, img);
-  Fl_X::q_end_image();
-  CFRelease(img);
+  if (img) {
+    CGRect rect = { { dest_x, dest_y }, { src_w, src_h } };
+    Fl_X::q_begin_image(rect, 0, 0, src_w, src_h);
+    CGContextDrawImage(fl_gc, rect, img);
+    Fl_X::q_end_image();
+    CFRelease(img);
+    }
 #else
 # error unsupported platform
 #endif