config.c: #include of non-existent file should not crash

Corrects a segmentation fault when a configuration file has a #include
statement that referenced a file that does not exist.

Resolves: https://github.com/asterisk/asterisk/issues/1139
(cherry picked from commit ffb0969a98)

main/config.c

@@ -2232,7 +2232,6 @@ static int process_text_line(struct ast_config *cfg, struct ast_category **cat,
 		}
 		if (!result && (include_type != CONFIG_STATEMENT_TRYINCLUDE)) {
 			ast_log(LOG_ERROR, "The file '%s' was listed as a #include but it does not exist.\n", cur);
-			ast_include_destroy(newinclude);
 			return -1;
 		}