WUtil: Fix non-closed file handle in WMWritePropListToFile

As reported by Coverity (CID #50129), in case of error during the write
operation, the failure path does include close of the file handle. In
addition to the resource leak, this may be a problem if the application
were to make a second try on the same file.

Signed-off-by: Christophe CURIS <christophe.curis@free.fr>

WINGs/proplist.c

@@ -1695,6 +1695,7 @@ Bool WMWritePropListToFile(WMPropList * plist, const char *path)
 	if (fprintf(theFile, "%s\n", desc) != strlen(desc) + 1) {
 		werror(_("writing to file: %s failed"), thePath);
 		wfree(desc);
+		fclose(theFile);
 		goto failure;
 	}