fix double free on tiff write

if you attached a profile to a tiff from a file during write, you'd get
a double-free

see https://github.com/jcupitt/libvips/issues/371

ChangeLog

@@ -7,6 +7,7 @@
 - use builtin isnan isinf when possible [Lovell Fuller]
 - tune vips_shrinkh(), 30% faster [Lovell Fuller]
 - remove SEQ hint from vips_subsample(), fixes cli performance [erdmann]
+- fix double free on attach ICC profile from file in tiff write [erdmann]
 
 1/1/16 started 8.2.1
 - add a compat stub [Benjamin Gilbert]

libvips/foreign/vips2tiff.c

@@ -888,7 +888,7 @@ write_new( VipsImage *im, const char *filename,
 	write->pyramid = pyramid;
 	write->onebit = squash;
 	write->miniswhite = miniswhite;
-	write->icc_profile = profile;
+	write->icc_profile = vips_strdup( NULL, profile );
 	write->bigtiff = bigtiff;
 	write->rgbjpeg = rgbjpeg;
 	write->properties = properties;