[gnumeric] xls: prevent critical.

[Morten Welinder <mortenw src gnome org>]

commit 9cc923f3a1fb1e93c44ccbd772bac2c2b383c761
Author: Morten Welinder <terra gnome org>
Date:   Mon Nov 20 19:15:28 2017 -0500

    xls: prevent critical.

 plugins/excel/ChangeLog          |    6 ++++++
 plugins/excel/ms-formula-write.c |    6 ++++--
 2 files changed, 10 insertions(+), 2 deletions(-)
---
diff --git a/plugins/excel/ChangeLog b/plugins/excel/ChangeLog
index 8569a1e..ffa9586 100644
--- a/plugins/excel/ChangeLog
+++ b/plugins/excel/ChangeLog
@@ -1,3 +1,9 @@
+2017-11-20  Morten Welinder  <terra gnome org>
+
+       * ms-formula-write.c (xl_map_char_to_type): Improve debug output.
+       (write_funcall): Avoid a critical for ERROR function.  This might
+       not be right -- need to check what XL wants for this.
+
 2017-11-18  Morten Welinder <terra gnome org>
 
        * Release 1.12.36
diff --git a/plugins/excel/ms-formula-write.c b/plugins/excel/ms-formula-write.c
index 0111b5b..de93246 100644
--- a/plugins/excel/ms-formula-write.c
+++ b/plugins/excel/ms-formula-write.c
@@ -231,7 +231,7 @@ xl_map_char_to_type (char t)
                return XL_ARRAY;
        if (t == 'v')
                return XL_ROOT;
-       g_warning ("unknown op class '%c' assuming val", t);
+       g_warning ("unknown op class '%c' assuming val", t ? t : '-');
        return XL_VAL;
 }
 
@@ -553,7 +553,9 @@ write_funcall (PolishData *pd, GnmExpr const *expr,
                min_args = ef->efunc->min_args;
                max_args = ef->efunc->max_args;
                func_idx = ef->efunc->idx;
-               func_type = xl_map_char_to_type (ef->efunc->type);
+               func_type = ef->efunc->type
+                       ? xl_map_char_to_type (ef->efunc->type)
+                       : XL_VAL; // Assumption
                arg_types = ef->efunc->known_args;
        } else {
                min_args = max_args = expr->func.argc;