[truetype] Fix error handling for embedded bitmaps.

Problem reported by Hin-Tak Leung <htl10@users.sourceforge.net>.

* src/truetype/ttgload.c (TT_Load_Glyph)
[TT_CONFIG_OPTION_EMBEDDED_BITMAPS]: Handle error if font is not
scalable.

ChangeLog

@@ -1,3 +1,13 @@
+2017-05-15  Werner Lemberg  <wl@gnu.org>
+
+	[truetype] Fix error handling for embedded bitmaps.
+
+	Problem reported by Hin-Tak Leung <htl10@users.sourceforge.net>.
+
+	* src/truetype/ttgload.c (TT_Load_Glyph)
+	[TT_CONFIG_OPTION_EMBEDDED_BITMAPS]: Handle error if font is not
+	scalable.
+
 2017-05-15  Alexei Podtelezhnikov  <apodtele@gmail.com>
 
 	[autofit] Make autohint warping NORMAL option.

src/truetype/ttgload.c

@@ -2621,7 +2621,13 @@
          IS_DEFAULT_INSTANCE                     )
     {
       error = load_sbit_image( size, glyph, glyph_index, load_flags );
-      if ( !error )
+      if ( error )
+      {
+        /* return error if font is not scalable */
+        if ( !FT_IS_SCALABLE( glyph->face ) )
+          return error;
+      }
+      else
       {
         if ( FT_IS_SCALABLE( glyph->face ) )
         {