eeschema, sim: clean signal list when last panel is closed
Function SIM_PLOT_FRAME::GetCurrentPlot() doesn't return nullptr in onPlotClose() callbacks, when last plot was closed. It needed to be worked-around.
Fixes: #9119 (closed)
Function SIM_PLOT_FRAME::GetCurrentPlot() doesn't return nullptr in onPlotClose() callbacks, when last plot was closed. It needed to be worked-around.
Fixes: #9119 (closed)