res_http_websocket.c: Fix incorrect use of sizeof in ast_websocket_write().

This won't fix the reported issue but it is an incorrect use of sizeof.

ASTERISK-24566
Reported by:  Badalian Vyacheslav
........

Merged revisions 429867 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/13@429868 65c4cc65-6c06-0410-ace0-fbb531ad65f3

res/res_http_websocket.c

@@ -273,7 +273,7 @@ int AST_OPTIONAL_API_NAME(ast_websocket_write)(struct ast_websocket *session, en
 {
 	size_t header_size = 2; /* The minimum size of a websocket frame is 2 bytes */
 	char *frame;
-	uint64_t length = 0;
+	uint64_t length;
 
 	if (actual_length < 126) {
 		length = actual_length;
@@ -288,7 +288,7 @@ int AST_OPTIONAL_API_NAME(ast_websocket_write)(struct ast_websocket *session, en
 	}
 
 	frame = ast_alloca(header_size);
-	memset(frame, 0, sizeof(*frame));
+	memset(frame, 0, header_size);
 
 	frame[0] = opcode | 0x80;
 	frame[1] = length;