[gnumeric] Conditional Formatting: fix crash [#361]

[Morten Welinder <mortenw src gnome org>]

commit d6c9876cf2f7e6e011cda91098449919f5d64ca6
Author: Morten Welinder <terra gnome org>
Date:   Wed Oct 24 15:03:39 2018 -0400

    Conditional Formatting: fix crash [#361]

 src/style-conditions.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/style-conditions.c b/src/style-conditions.c
index 0769bb18c..417548c3e 100644
--- a/src/style-conditions.c
+++ b/src/style-conditions.c
@@ -985,7 +985,7 @@ gnm_style_conditions_eval (GnmStyleConditions const *sc, GnmEvalPos const *ep)
        g_return_val_if_fail (sc->conditions != NULL, -1);
 
        cell = sheet_cell_get (ep->sheet, ep->eval.col, ep->eval.row);
-       cv = value_dup (cell->value);
+       cv = cell ? value_dup (cell->value) : NULL;
 
        conds = sc->conditions;