[truetype] Fix multiple calls of `FT_Get_MM_Var' (#52955).

* src/truetype/ttgxvar.c (TT_Get_MM_Var): Set
`face->blend->num_axis' in case we have to initialize the
`face->blend'.

ChangeLog

@@ -1,3 +1,11 @@
+2018-01-26  Ben Wagner  <bungeman@google.com>
+
+	[truetype] Fix multiple calls of `FT_Get_MM_Var' (#52955).
+
+	* src/truetype/ttgxvar.c (TT_Get_MM_Var): Set
+	`face->blend->num_axis' in case we have to initialize the
+	`face->blend'.
+
 2018-01-23  Alexei Podtelezhnikov  <apodtele@gmail.com>
 
 	[apinames] Anonymous version map for GNU linker.

src/truetype/ttgxvar.c

@@ -2048,7 +2048,8 @@
       if ( FT_NEW( face->blend ) )
         goto Exit;
 
-      num_axes = fvar_head.axisCount;
+      num_axes              = fvar_head.axisCount;
+      face->blend->num_axis = num_axes;
     }
     else
       num_axes = face->blend->num_axis;