preview_window: check xctx valid before calling resetwin()

src/xinit.c

@@ -1267,7 +1267,7 @@ int preview_window(const char *what, const char *win_path, const char *fname)
         dbg(1, "preview_window() draw, load schematic\n");
         load_schematic(1,fname, 0, 1);
       } else {
-        resetwin(1, 1, 0, 0, 0);  /* resetwin(create_pixmap, clear_pixmap, force) */
+        if(xctx) resetwin(1, 1, 0, 0, 0);  /* resetwin(create_pixmap, clear_pixmap, force) */
       }
       zoom_full(1, 0, 1 + 2 * tclgetboolvar("zoom_full_center"), 0.97); /* draw */
       xctx = save_xctx;

src/xschem.tcl

@@ -8582,6 +8582,19 @@ global env has_x OS autofocus_mainwindow
       bind $topwin <ButtonPress> "xschem callback %W %T %x %y 0 %b 0 %s"
     }
     bind $topwin <ButtonRelease> "xschem callback %W %T %x %y 0 %b 0 %s"
+
+    #### test: show keybindings
+    # bind $topwin <KeyPress-slash> "
+    #   if {!\[info exists bindkeys\]} {
+    #     set bindkeys 1
+    #     xschem preview_window create $topwin
+    #     xschem preview_window draw $topwin [abs_sym_path bindkeys_cheatsheet.sym]
+    #   } else {
+    #     unset bindkeys
+    #     xschem preview_window $topwin close 
+    #     xschem redraw
+    #   }
+    # "
     bind $topwin <KeyPress> "
       if {{%K} eq {Escape}} { destroy .ctxmenu }
       xschem callback %W %T %x %y %N 0 0 %s"