fix bogus complaints about missing Store/Account references

... when the reference is simply invalid (we already get a complaint
about that).

src/config.c

@@ -505,6 +505,7 @@ load_config( const char *where )
 							goto stpcom;
 						}
 					}
+					channel->stores[fn] = (void *)~0;
 					error( "%s:%d: unknown store '%s'\n",
 					       cfile.file, cfile.line, cfile.val + 1 );
 					cfile.err = 1;

src/drv_imap.c

@@ -3679,6 +3679,7 @@ imap_parse_store( conffile_t *cfg, store_conf_t **storep )
 				for (srv = servers; srv; srv = srv->next)
 					if (srv->name && !strcmp( srv->name, cfg->val ))
 						goto gotsrv;
+				store->server = (void *)~0;
 				error( "%s:%d: unknown IMAP account '%s'\n", cfg->file, cfg->line, cfg->val );
 				cfg->err = 1;
 				continue;