stop parsing config lines after invalid keyword

otherwise we may pointlessly complain about excess tokens.

src/config.c

@@ -475,6 +475,7 @@ load_config( const char *where )
 				} else if (!getopt_helper( &cfile, &cops, channel )) {
 					error( "%s:%d: keyword '%s' is not recognized in Channel sections\n",
 					       cfile.file, cfile.line, cfile.cmd );
+					cfile.rest = NULL;
 					cfile.err = 1;
 				}
 			}
@@ -522,6 +523,7 @@ load_config( const char *where )
 				} else {
 					error( "%s:%d: keyword '%s' is not recognized in Group sections\n",
 					       cfile.file, cfile.line, cfile.cmd );
+					cfile.rest = NULL;
 					cfile.err = 1;
 				}
 			}
@@ -550,6 +552,7 @@ load_config( const char *where )
 			error( "%s:%d: '%s' is not a recognized section-starting or global keyword\n",
 			       cfile.file, cfile.line, cfile.cmd );
 			cfile.err = 1;
+			cfile.rest = NULL;
 			while (getcline( &cfile ))
 				if (!cfile.cmd)
 					goto reloop;

src/driver.c

@@ -77,6 +77,7 @@ parse_generic_store( store_conf_t *store, conffile_t *cfg, const char *type )
 		store->flat_delim = nfstrdup( cfg->val );
 	} else {
 		error( "%s:%d: keyword '%s' is not recognized in %s sections\n", cfg->file, cfg->line, cfg->cmd, type );
+		cfg->rest = NULL;
 		cfg->err = 1;
 	}
 }

src/drv_imap.c

@@ -3704,6 +3704,7 @@ imap_parse_store( conffile_t *cfg, store_conf_t **storep )
 		} else {
 			error( "%s:%d: keyword '%s' is not recognized in IMAPAccount sections\n",
 			       cfg->file, cfg->line, cfg->cmd );
+			cfg->rest = NULL;
 			cfg->err = 1;
 			continue;
 		}