Fixed bug in handling null metadata

Makefile

@@ -1,4 +1,4 @@
-VERSION := 2.04
+VERSION := 2.05
 CC      := gcc
 CFLAGS  := -Wall -fPIC -fPIE 
 LDFLAGS := -pie -s

README.md

@@ -1,6 +1,6 @@
 # epub2txt -- Extract text from EPUB documents  
 
-Version 2.04, April 2022 
+Version 2.05, May 2022 
 
 ## What is this? 
 
@@ -232,6 +232,7 @@ even approximately, in ASCII.
 
 Date | Change
 -----|-------
+2.05, Apr 2022 | Fixed bug with empty metadata tags 
 2.04, Apr 2022 | Improved handling of UTF-8 BOMs 
 2.03, Jan 2022 | Fixed a buffer overrun bug 
 2.02, May 2020 | Updated XML parser 

man1/epub2txt.1

@@ -3,7 +3,7 @@
 .\" redistribute this software so long as all of the original files are
 .\" included, and that this copyright notice is retained.
 .\"
-.TH epub2txt 1 "April 2022"
+.TH epub2txt 1 "May 2022"
 .SH NAME
 epub2txt \- Extract text from EPUB documents 
 .SH SYNOPSIS

src/epub2txt.c

@@ -89,14 +89,22 @@ static char *epub2txt_unescape_html (const char *s)
 static void epub2txt_format_meta (const Epub2TxtOptions *options, 
           const char *key, const char *text)
   {
-  char *ss = epub2txt_unescape_html (text);
-  char *s;
-  asprintf (&s, "%s: %s", key, ss);
-  char *error = NULL;
-  xhtml_utf8_to_stdout (s, options, &error);
-  if (error) free (error);
-  free (s);
-  free (ss);
+  // text ends up "null" here, if the meta tag had no content (which should
+  //   not happen, but we don't want to crash if it does). I suppress all
+  //   output in this case, but perhaps it would be better to print the
+  //   metadata key, and the value "null", or "empty"? I can't really predict
+  //   what a user would prefer to see.
+  if (text)
+    {
+    char *ss = epub2txt_unescape_html (text);
+    char *s;
+    asprintf (&s, "%s: %s", key, ss);
+    char *error = NULL;
+    xhtml_utf8_to_stdout (s, options, &error);
+    if (error) free (error);
+    free (s);
+    free (ss);
+    }
   }