Throw an error when a chatnet has no available url

If you type /connect <CN> and the chatnet <CN> has no url available
let's just throw an error instead of trying to process <CN> as a url.

src/core/chat-commands.c

@@ -73,6 +73,13 @@ static SERVER_CONNECT_REC *get_server_connect(const char *data, int *plus_addr,
 
 	conn = server_create_conn(proto != NULL ? proto->id : -1, addr,
 				  atoi(portstr), chatnet, password, nick);
+	if (conn == NULL) {
+		signal_emit("error command", 1,
+			    GINT_TO_POINTER(CMDERR_NO_SERVER_DEFINED));
+		cmd_params_free(free_arg);
+		return NULL;
+	}
+
 	if (proto == NULL)
 		proto = chat_protocol_find_id(conn->chat_type);
 

src/core/commands.h

@@ -41,7 +41,8 @@ enum {
 	CMDERR_INVALID_TIME, /* invalid time specification */
 	CMDERR_INVALID_CHARSET, /* invalid charset specification */
 	CMDERR_EVAL_MAX_RECURSE, /* eval hit recursion limit */
-	CMDERR_PROGRAM_NOT_FOUND /* program not found */
+	CMDERR_PROGRAM_NOT_FOUND, /* program not found */
+	CMDERR_NO_SERVER_DEFINED, /* no server has been defined for a given chatnet */
 };
 
 /* Return the full command for `alias' */

src/core/servers-setup.c

@@ -323,6 +323,8 @@ server_create_conn(int chat_type, const char *dest, int port,
 		rec = create_chatnet_conn(chatrec->name, port, password, nick);
 		if (rec != NULL)
 			return rec;
+		/* The chatnet has no url to connect to */
+		return NULL;
 	}
 
 	chatrec = chatnet == NULL ? NULL : chatnet_find(chatnet);

src/fe-common/core/fe-core-commands.c

@@ -51,7 +51,8 @@ static int ret_texts[] = {
         TXT_INVALID_TIME,
         TXT_INVALID_CHARSET,
         TXT_EVAL_MAX_RECURSE,
-        TXT_PROGRAM_NOT_FOUND
+        TXT_PROGRAM_NOT_FOUND,
+	TXT_NO_SERVER_DEFINED,
 };
 
 int command_hide_output;

src/fe-common/core/module-formats.c

@@ -223,6 +223,7 @@ FORMAT_REC fecommon_core_formats[] = {
 	{ "invalid_charset", "Invalid charset: $0", 1, { 0 } },
 	{ "eval_max_recurse", "/eval hit maximum recursion limit", 0 },
 	{ "program_not_found", "Could not find file or file is not executable", 0 },
+	{ "no_server_defined", "No servers defined for this network, see /help server for how to add one", 0 },
 
 	/* ---- */
 	{ NULL, "Themes", 0 },

src/fe-common/core/module-formats.h

@@ -192,6 +192,7 @@ enum {
 	TXT_INVALID_CHARSET,
 	TXT_EVAL_MAX_RECURSE,
 	TXT_PROGRAM_NOT_FOUND,
+	TXT_NO_SERVER_DEFINED,
 
 	TXT_FILL_11,