fix a segv with old-style interpolate CLI args

thanks Nicolas

TODO

@@ -2,25 +2,12 @@
 
 
 
-
-
-- try:
-
-	$ vips im_affinei original.png vipsnohalo.png nohalo 4 0 0 4 1.5 1.5 0 0 1600 1200
-	Segmentation fault
-
-  in master
-
-
-
-
 - look at libpeas for plugin support
 
 	http://live.gnome.org/Libpeas
 
 
 
-
 - foreign docs come up as "VipsForeignSave", annoying, why?
 
 - we can no longer have round brackets in filenames, argh

libvips/deprecated/dispatch_types.c

@@ -870,10 +870,13 @@ im_type_desc im__output_gvalue = {
 static int
 input_interpolate_init( im_object *obj, char *str )
 {
-	VipsObjectClass *interpolate_class;
+	GType type = g_type_from_name( "VipsInterpolate" );
+	VipsObjectClass *interpolate_class = 
+		VIPS_INTERPOLATE_CLASS( g_type_class_ref( type ) );
 	VipsObject *object;
 
-	interpolate_class = vips_class_find( "VipsInterpolate", "interpolate" );
+	g_assert( interpolate_class );
+
 	if( !(object = vips_object_new_from_string( interpolate_class, str )) )
 		return( -1 );
 	if( vips_object_build( object ) ) {

libvips/iofuncs/object.c

@@ -1680,6 +1680,7 @@ vips_object_new_from_string( VipsObjectClass *object_class, const char *p )
 	VipsObject *object;
 	VipsToken token;
 
+	g_assert( object_class );
 	g_assert( object_class->new_from_string );
 
 	/* The first string in p is the main construct arg, eg. a filename.
@@ -1893,14 +1894,14 @@ vips_type_map_all( GType base, VipsTypeMapFn fn, void *a )
 /**
  * vips_class_map_all: (skip) 
  *
- * Loop over all the subclasses of a base type. Non-abtract classes only.
+ * Loop over all the subclasses of a base type. Non-abstract classes only.
  */
 void *
 vips_class_map_all( GType type, VipsClassMapFn fn, void *a )
 {
 	void *result;
 
-	/* We can't instantiate abstract classes.
+	/* Avoid abstract classes. Use type_map_all for them.
 	 */
 	if( !G_TYPE_IS_ABSTRACT( type ) ) {
 		/* We never unref this ref, but we never unload classes