[gnome-calculator] Return with failure exitcode in case of precision error (bgo#749336)

[Robert Roth <robertroth src gnome org>]

commit c80831ecba06757736aab395f1301a2af5eb4468
Author: Robert Roth <robert roth off gmail com>
Date:   Wed Jan 24 02:13:32 2018 +0200

    Return with failure exitcode in case of precision error (bgo#749336)

 src/gnome-calculator.vala |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)
---
diff --git a/src/gnome-calculator.vala b/src/gnome-calculator.vala
index d5305bc..079ec6e 100644
--- a/src/gnome-calculator.vala
+++ b/src/gnome-calculator.vala
@@ -232,7 +232,13 @@ public class Calculator : Gtk.Application
             {
                 var serializer = new Serializer (DisplayFormat.AUTOMATIC, 10, 9);
                 serializer.set_representation_base (representation_base);
-                stdout.printf ("%s\n", serializer.to_string (result));
+                var eq_result = serializer.to_string (result);
+                if (serializer.error != null) {
+                    stderr.printf (serializer.error);
+                    return Posix.EXIT_FAILURE;
+                }
+
+                stdout.printf ("%s\n", eq_result);
                 return Posix.EXIT_SUCCESS;
             }
             else if (error == ErrorCode.MP)