am: close input stream even in case of an error

Reported via Coverity.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

builtin/am.c

@@ -762,9 +762,11 @@ static int split_mail_conv(mail_conv_fn fn, struct am_state *state,
 		mail = mkpath("%s/%0*d", state->dir, state->prec, i + 1);
 
 		out = fopen(mail, "w");
-		if (!out)
+		if (!out) {
+			fclose(in);
 			return error_errno(_("could not open '%s' for writing"),
 					   mail);
+		}
 
 		ret = fn(out, in, keep_cr);