Prevent a use-after-free in pmchart, found on Win32.
Prevent a use-after-free in pmchart, found on Win32.

When resizing a window after the deletion of a chart, we
were deleting the chart and then asking it for its height
in the readjust-the-main-window-size calculation... segv.

tjanez/pcp,andyvand/cygpcpfans,edwardt/pcp,adfernandes/pcp,aeg-aeg/pcpfans,prasincs/pcp,adfernandes/pcp,tjanez/pcp,tjanez/pcp,aeg-aeg/pcpfans,wuliming/pcp,wuliming/pcp,andyvand/cygpcpfans,prasincs/pcp,wuliming/pcp,edwardt/pcp,andyvand/cygpcpfans,prasincs/pcp,aeg-aeg/pcpfans,adfernandes/pcp,prasincs/pcp,wuliming/pcp,adfernandes/pcp,mbaldessari/pcp,edwardt/pcp,prasincs/pcp,aeg-aeg/pcpfans,andyvand/cygpcpfans,mbaldessari/pcp,aeg-aeg/pcpfans,mbaldessari/pcp,andyvand/cygpcpfans,adfernandes/pcp,tjanez/pcp,prasincs/pcp,andyvand/cygpcpfans,wuliming/pcp,andyvand/cygpcpfans,tjanez/pcp,tjanez/pcp,mbaldessari/pcp,adfernandes/pcp,edwardt/pcp,aeg-aeg/pcpfans,mbaldessari/pcp,tjanez/pcp,andyvand/cygpcpfans,mbaldessari/pcp,wuliming/pcp,wuliming/pcp,prasincs/pcp,wuliming/pcp,aeg-aeg/pcpfans,adfernandes/pcp,edwardt/pcp,tjanez/pcp,edwardt/pcp,edwardt/pcp,adfernandes/pcp,edwardt/pcp,prasincs/pcp,aeg-aeg/pcpfans