libsemanage: Fix USE_AFTER_FREE (CWE-672) in semanage_direct_write_langext()

>From fclose(3):
Upon successful completion, 0 is returned.  Otherwise, EOF is returned
and errno is set to indicate the error. In either case, any further
access (including another call to fclose()) to the stream results in
undefined behavior.

Fixes:
    Error: USE_AFTER_FREE (CWE-672): [#def1]
    libsemanage-3.2/src/direct_api.c:1023: freed_arg: "fclose" frees "fp".
    libsemanage-3.2/src/direct_api.c:1034: use_closed_file: Calling "fclose" uses file handle "fp" after closing it.
    # 1032|
    # 1033|   cleanup:
    # 1034|-> 	if (fp != NULL) fclose(fp);
    # 1035|
    # 1036|   	return ret;

Signed-off-by: Petr Lautrbach <plautrba@redhat.com>

libsemanage/src/direct_api.c

@@ -1022,6 +1022,7 @@ static int semanage_direct_write_langext(semanage_handle_t *sh,
 
 	if (fclose(fp) != 0) {
 		ERR(sh, "Unable to close %s module ext file.", modinfo->name);
+		fp = NULL;
 		ret = -1;
 		goto cleanup;
 	}