[gcalctool] Fix conversions

[Robert Ancell <rancell src gnome org>]

commit 2b19afcfacf50461bf2b56b2026cb8a4250fcbba
Author: Robert Ancell <robert ancell canonical com>
Date:   Mon Nov 29 14:10:20 2010 +1100

    Fix conversions

 src/mp-equation.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/mp-equation.c b/src/mp-equation.c
index 1e443ab..9e136ca 100644
--- a/src/mp-equation.c
+++ b/src/mp-equation.c
@@ -250,9 +250,9 @@ static int
 convert(MPEquationParserState *state, const MPNumber *x, const char *x_units, const char *z_units, MPNumber *z)
 {
     if (!units_convert(x, x_units, z_units, z))
-        return 1;
+        return 0;
 
-    return 0;
+    return 1;
 }