string-util: imply NULL termination of strextend() argument list

The trailing NULL in the argument list is now implied (similar to
what we already have in place in strjoin()).

src/shared/bus-unit-util.c

@@ -1159,7 +1159,7 @@ static int bus_append_execute_property(sd_bus_message *m, const char *field, con
                 if (r < 0)
                         return log_error_errno(r, "Failed to unescape text '%s': %m", eq);
 
-                if (!strextend(&unescaped, "\n", NULL))
+                if (!strextend(&unescaped, "\n"))
                         return log_oom();
 
                 /* Note that we don't expand specifiers here, but that should be OK, as this is a programmatic

src/shared/conf-parser.c

@@ -343,7 +343,7 @@ int config_parse(
                                 return -ENOBUFS;
                         }
 
-                        if (!strextend(&continuation, l, NULL)) {
+                        if (!strextend(&continuation, l)) {
                                 if (flags & CONFIG_PARSE_WARN)
                                         log_oom();
                                 return -ENOMEM;

src/shared/dissect-image.c

@@ -1340,12 +1340,12 @@ static int mount_partition(
                 if (asprintf(&uid_option, "uid=" UID_FMT ",gid=" GID_FMT, uid_shift, (gid_t) uid_shift) < 0)
                         return -ENOMEM;
 
-                if (!strextend_with_separator(&options, ",", uid_option, NULL))
+                if (!strextend_with_separator(&options, ",", uid_option))
                         return -ENOMEM;
         }
 
         if (!isempty(m->mount_options))
-                if (!strextend_with_separator(&options, ",", m->mount_options, NULL))
+                if (!strextend_with_separator(&options, ",", m->mount_options))
                         return -ENOMEM;
 
         if (FLAGS_SET(flags, DISSECT_IMAGE_MKDIR)) {

src/shared/mount-util.c

@@ -733,7 +733,7 @@ int mount_option_mangle(
                 }
 
                 /* If 'word' is not a mount flag, then store it in '*ret_remaining_options'. */
-                if (!ent->name && !strextend_with_separator(&ret, ",", word, NULL))
+                if (!ent->name && !strextend_with_separator(&ret, ",", word))
                         return -ENOMEM;
         }
 

src/shared/nsflags.c

@@ -61,7 +61,7 @@ int namespace_flags_to_string(unsigned long flags, char **ret) {
                 if ((flags & namespace_flag_map[i].flag) != namespace_flag_map[i].flag)
                         continue;
 
-                if (!strextend_with_separator(&s, " ", namespace_flag_map[i].name, NULL))
+                if (!strextend_with_separator(&s, " ", namespace_flag_map[i].name))
                         return -ENOMEM;
         }