dpkg-deb: Fix corrupt archive header magic error string

The string was referring to the first header when the string refers to
any header parsed.

dpkg-deb/extract.c

@@ -143,7 +143,7 @@ extracthalf(const char *debar, const char *dir, const char *taroption,
       dpkg_ar_normalize_name(&arh);
 
       if (memcmp(arh.ar_fmag,ARFMAG,sizeof(arh.ar_fmag)))
-        ohshit(_("file `%.250s' is corrupt - bad magic at end of first header"),debar);
+        ohshit(_("file '%.250s' is corrupt - bad archive header magic"), debar);
       memberlen = dpkg_ar_member_get_size(debar, &arh);
       if (!header_done) {
         char *infobuf;