[pango] Fix warnings if font is not found

[Behdad Esfahbod <behdad src gnome org>]

commit b110042886198dc51b82d1f9d4c957121ee336eb
Author: Behdad Esfahbod <behdad behdad org>
Date:   Fri Apr 10 10:24:55 2015 -0700

    Fix warnings if font is not found

 pango/fonts.c        |    3 ++-
 pango/pango-engine.c |    4 ++--
 2 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/pango/fonts.c b/pango/fonts.c
index 52ef72d..6b7d949 100644
--- a/pango/fonts.c
+++ b/pango/fonts.c
@@ -1558,7 +1558,8 @@ pango_font_find_shaper (PangoFont     *font,
 {
   PangoEngineShape* shaper;
 
-  g_return_val_if_fail (font != NULL, NULL);
+  if (G_UNLIKELY (!font))
+    return NULL;
 
   shaper = PANGO_FONT_GET_CLASS (font)->find_shaper (font, language, ch);
 
diff --git a/pango/pango-engine.c b/pango/pango-engine.c
index 777132b..f2797e4 100644
--- a/pango/pango-engine.c
+++ b/pango/pango-engine.c
@@ -153,8 +153,8 @@ _pango_engine_shape_covers (PangoEngineShape *engine,
                            PangoLanguage    *language,
                            gunichar          wc)
 {
-  g_return_val_if_fail (PANGO_IS_ENGINE_SHAPE (engine), PANGO_COVERAGE_NONE);
-  g_return_val_if_fail (PANGO_IS_FONT (font), PANGO_COVERAGE_NONE);
+  if (G_UNLIKELY (!engine || !font))
+    return PANGO_COVERAGE_NONE;
 
   return PANGO_ENGINE_SHAPE_GET_CLASS (engine)->covers (engine,
                                                        font,