[gimp] plug-ins: fix some build warning.

[Jehan <jehanp src gnome org>]

commit b71754f2a7c32f9ada99731a2e8334a98dcf6e73
Author: Jehan <jehan girinstud io>
Date:   Mon Apr 13 21:54:09 2020 +0200

    plug-ins: fix some build warning.
    
    Fixes:
    > warning: using integer absolute value function ‘abs’ when argument is of floating point type ‘double’ 
[-Wabsolute-value]

 plug-ins/common/curve-bend.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/plug-ins/common/curve-bend.c b/plug-ins/common/curve-bend.c
index 748d57675e..44c47b2ea2 100644
--- a/plug-ins/common/curve-bend.c
+++ b/plug-ins/common/curve-bend.c
@@ -2079,9 +2079,9 @@ bender_graph_events (GtkWidget    *widget,
   for (i = 0; i < 17; i++)
     {
       if (cd->points[cd->outline][i][0] != -1)
-        if (abs (x - (cd->points[cd->outline][i][0] * 255.0)) < distance)
+        if (abs ((int) (x - (cd->points[cd->outline][i][0] * 255.0))) < distance)
           {
-            distance = abs (x - (cd->points[cd->outline][i][0] * 255.0));
+            distance = abs ((int) (x - (cd->points[cd->outline][i][0] * 255.0)));
             closest_point = i;
           }
     }