http: Prevent script errors when http$current_entity is not set

The current_entity tracking in HTTP assumes that client/server never
send HTTP entities at the same time. The attached pcap (generated
artificially) violates this and triggers:

    1663698249.307259 expression error in <...>base/protocols/http/./entities.zeek, line 89: field value missing (HTTP::c$http$current_entity)

For the http-no-crlf test, include weird.log as baseline. Now that weird is
@load'ed from http, it is actually created and seems to make sense
to btest-diff it, too.

scripts/base/protocols/http/entities.zeek

@@ -1,6 +1,7 @@
 ##! Analysis and logging for MIME entities found in HTTP sessions.
 
 @load base/frameworks/files
+@load base/frameworks/notice/weird
 @load base/utils/strings
 @load base/utils/files
 @load ./main
@@ -83,6 +84,19 @@ event http_begin_entity(c: connection, is_orig: bool) &priority=10
 
 event http_header(c: connection, is_orig: bool, name: string, value: string) &priority=3
 	{
+	if ( ! c$http?$current_entity )
+		{
+		local weird = Weird::Info(
+			$ts=network_time(),
+			$name="missing_HTTP_entity",
+			$uid=c$uid,
+			$id=c$id,
+			$source="HTTP"
+		);
+		Weird::weird(weird);
+		return;
+		}
+
 	if ( name == "CONTENT-DISPOSITION" &&
 	     /[fF][iI][lL][eE][nN][aA][mM][eE]/ in value )
 		{

testing/btest/Baseline/scripts.base.protocols.http.http-no-crlf/weird.log

@@ -0,0 +1,11 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+#separator \x09
+#set_separator	,
+#empty_field	(empty)
+#unset_field	-
+#path	weird
+#open XXXX-XX-XX-XX-XX-XX
+#fields	ts	uid	id.orig_h	id.orig_p	id.resp_h	id.resp_p	name	addl	notice	peer	source
+#types	time	string	addr	port	addr	port	string	string	bool	string	string
+XXXXXXXXXX.XXXXXX	CHhAvVGS1DHFjwGM9	10.1.6.206	49783	5.2.136.90	80	line_terminated_without_CRLF	-	F	zeek	CONTENTLINE
+#close XXXX-XX-XX-XX-XX-XX

testing/btest/Baseline/scripts.base.protocols.http.missing-http-entity/http.log

@@ -0,0 +1,11 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+#separator \x09
+#set_separator	,
+#empty_field	(empty)
+#unset_field	-
+#path	http
+#open XXXX-XX-XX-XX-XX-XX
+#fields	ts	uid	id.orig_h	id.orig_p	id.resp_h	id.resp_p	trans_depth	method	host	uri	referrer	version	user_agent	origin	request_body_len	response_body_len	status_code	status_msg	info_code	info_msg	tags	username	password	proxied	orig_fuids	orig_filenames	orig_mime_types	resp_fuids	resp_filenames	resp_mime_types
+#types	time	string	addr	port	addr	port	count	string	string	string	string	string	string	string	count	count	count	string	count	string	set[enum]	string	string	set[string]	vector[string]	vector[string]	vector[string]	vector[string]	vector[string]	vector[string]
+XXXXXXXXXX.XXXXXX	CHhAvVGS1DHFjwGM9	127.0.0.1	35474	127.0.0.1	8080	1	POST	interleave.me	/	-	1.1	-	-	10	3	200	OK	-	-	(empty)	-	-	-	FtWn3S3nVYQ9iA3uu8	-	text/plain	F2bxt6qiQGYTYxTgg	-	-
+#close XXXX-XX-XX-XX-XX-XX

testing/btest/Baseline/scripts.base.protocols.http.missing-http-entity/weird.log

@@ -0,0 +1,11 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+#separator \x09
+#set_separator	,
+#empty_field	(empty)
+#unset_field	-
+#path	weird
+#open XXXX-XX-XX-XX-XX-XX
+#fields	ts	uid	id.orig_h	id.orig_p	id.resp_h	id.resp_p	name	addl	notice	peer	source
+#types	time	string	addr	port	addr	port	string	string	bool	string	string
+XXXXXXXXXX.XXXXXX	CHhAvVGS1DHFjwGM9	127.0.0.1	35474	127.0.0.1	8080	missing_HTTP_entity	-	F	zeek	HTTP
+#close XXXX-XX-XX-XX-XX-XX

testing/btest/scripts/base/protocols/http/http-no-crlf.zeek

@@ -3,7 +3,7 @@
 # @TEST-EXEC: zeek -b -r $TRACES/http/no_crlf.pcap %INPUT
 # @TEST-EXEC: btest-diff conn.log
 # @TEST-EXEC: btest-diff http.log
-# @TEST-EXEC: test ! -f weird.log
+# @TEST-EXEC: btest-diff weird.log
 
 @load base/protocols/conn
 @load base/protocols/http

testing/btest/scripts/base/protocols/http/missing-http-entity.zeek

@@ -0,0 +1,7 @@
+# @TEST-DOC: The server starts sending a response while the client is still uploading the POST payload. This causes http_header to be raised while no entity is set.
+# @TEST-EXEC: zeek -b -r $TRACES/http/interleaved-http-entity.pcap %INPUT
+# @TEST-EXEC: btest-diff http.log
+# @TEST-EXEC: btest-diff weird.log
+
+@load base/protocols/http
+@load base/frameworks/notice/weird