plug-ins: fix #8467 "incorrect value RichTIFFIPTC" when loading TIFF ...

created by Adobe Lightroom 5.1

Adobe products are known to write incorrect RichTIFFIPTC tags in TIFF
images.

Since libtiff correctly detects and handles this there is no real need
for end users to be warned. So instead of a warning we will only output
a message to stderr.

plug-ins/file-tiff/file-tiff-io.c

@@ -200,6 +200,28 @@ tiff_io_warning (const gchar *module,
 
       va_end (ap_test);
     }
+  else if (! strcmp (fmt, "Incorrect value for \"%s\"; tag ignored"))
+    {
+      va_list ap_test;
+      const char *stag;
+
+      G_VA_COPY (ap_test, ap);
+
+      stag = va_arg (ap_test, const char *);
+
+      if (! strcmp (stag, "RichTIFFIPTC"))
+        {
+          gchar *msg = g_strdup_vprintf (fmt, ap);
+
+          /* This is an error in Adobe products. Just report to stderr. */
+          g_printerr ("[%s] %s\n", module, msg);
+          g_free (msg);
+
+          return;
+        }
+
+      va_end (ap_test);
+    }
 
   /* Workaround for: http://bugzilla.gnome.org/show_bug.cgi?id=131975
    * Ignore the warnings about unregistered private tags (>= 32768).