AP: Check Disassoc_Timer value

This must not be negative.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
diff --git a/ap.c b/ap.c
index 9ecb7de..c20a8e1 100644
--- a/ap.c
+++ b/ap.c
@@ -8149,6 +8149,12 @@
 		disassoc_timer = atoi(val);
 	else
 		disassoc_timer = dut->ap_disassoc_timer;
+	if (disassoc_timer < 0) {
+		sigma_dut_print(dut, DUT_MSG_ERROR,
+				"Invalid Disassoc_Timer value %d",
+				disassoc_timer);
+		return -1;
+	}
 
 	val = get_param(cmd, "Cand_List");
 	if (val && val[0])