[gtk] gdk: Protect against negative GDK_SCALE values

[Timm Bäder <baedert src gnome org>]

commit 09f04633caa169422ee02f23cd50bf4a73ca2184
Author: Timm Bäder <mail baedert org>
Date:   Sat Apr 7 10:05:38 2018 +0200

    gdk: Protect against negative GDK_SCALE values
    
    Using those should not happen.

 gdk/win32/gdkdisplay-win32.c | 2 +-
 gdk/x11/gdkscreen-x11.c      | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/gdk/win32/gdkdisplay-win32.c b/gdk/win32/gdkdisplay-win32.c
index 50d6fad098..9834b69cc7 100644
--- a/gdk/win32/gdkdisplay-win32.c
+++ b/gdk/win32/gdkdisplay-win32.c
@@ -912,7 +912,7 @@ gdk_win32_display_init (GdkWin32Display *display)
     {
       display->surface_scale = atol (scale_str);
 
-      if (display->surface_scale == 0)
+      if (display->surface_scale <= 0)
         display->surface_scale = 1;
 
       display->has_fixed_scale = TRUE;
diff --git a/gdk/x11/gdkscreen-x11.c b/gdk/x11/gdkscreen-x11.c
index 4554c6ccd4..f83df090e8 100644
--- a/gdk/x11/gdkscreen-x11.c
+++ b/gdk/x11/gdkscreen-x11.c
@@ -774,7 +774,7 @@ _gdk_x11_screen_new (GdkDisplay *display,
     {
       x11_screen->fixed_surface_scale = TRUE;
       x11_screen->surface_scale = atol (scale_str);
-      if (x11_screen->surface_scale == 0)
+      if (x11_screen->surface_scale <= 0)
         x11_screen->surface_scale = 1;
     }
   else