Properly handle a no-payload-selected scenario

scripts/resource/autoexploit.rc

@@ -94,7 +94,7 @@ def select_payload(exploit)
 	else
 		# WTF? This exploit supports NONE of our favorite payloads?
 		# What kinda BS is this?
-		return payload
+		return nil
 	end
 end
 
@@ -128,7 +128,12 @@ def auto_exploit(module_path)
 
 	get_payload = select_payload(exploit)
 	lhost       = Rex::Socket.source_address('50.50.50.50')
-	print_status("Payload selected: #{get_payload} (lhost=#{lhost})")
+
+	if get_payload.nil?
+		raise RuntimeError, "No payload selected for this exploit"
+	else
+		print_status("Payload selected: #{get_payload} (lhost=#{lhost})")
+	end
 
 	framework.db.workspace.vulns.each do |vuln|
 		next if not ref_has_match(vuln.refs, exploit_refs)