Allow utf8 in roster header char

This and the following commits should make a couple of more configs
allow utf8 chars so people can use their weird icons :-)

We did the same for the otr/omemo/pgp indicators at:
1f8b1eb740
5cf6ee1bc6

src/config/preferences.c

@@ -1080,32 +1080,30 @@ prefs_set_omemo_char(char* ch)
     return _prefs_set_encryption_char(ch, PREF_GROUP_OMEMO, "omemo.char");
 }
 
-char
+char*
 prefs_get_roster_header_char(void)
 {
-    char result = 0;
+    char* result = NULL;
 
     char* resultstr = g_key_file_get_string(prefs, PREF_GROUP_UI, "roster.header.char", NULL);
-    if (!resultstr) {
-        result = 0;
-    } else {
-        result = resultstr[0];
+    if (resultstr) {
+        result = resultstr;
     }
-    free(resultstr);
 
     return result;
 }
 
 void
-prefs_set_roster_header_char(char ch)
+prefs_set_roster_header_char(char* ch)
 {
-    char str[2];
-    str[0] = ch;
-    str[1] = '\0';
-
-    g_key_file_set_string(prefs, PREF_GROUP_UI, "roster.header.char", str);
+    if (g_utf8_strlen(ch, 4) == 1) {
+        g_key_file_set_string(prefs, PREF_GROUP_UI, "roster.header.char", ch);
+    } else {
+        log_error("Could not set roster header char: %s", ch);
+    }
 }
 
+
 void
 prefs_clear_roster_header_char(void)
 {

src/config/preferences.h

@@ -254,8 +254,8 @@ gboolean prefs_set_omemo_char(char* ch);
 char* prefs_get_ox_char(void);
 gboolean prefs_set_ox_char(char* ch);
 
-char prefs_get_roster_header_char(void);
-void prefs_set_roster_header_char(char ch);
+char* prefs_get_roster_header_char(void);
+void prefs_set_roster_header_char(char* ch);
 void prefs_clear_roster_header_char(void);
 char prefs_get_roster_contact_char(void);
 void prefs_set_roster_contact_char(char ch);

src/config/theme.c

@@ -422,8 +422,8 @@ _load_preferences(void)
 
     if (g_key_file_has_key(theme, "ui", "roster.header.char", NULL)) {
         gchar* ch = g_key_file_get_string(theme, "ui", "roster.header.char", NULL);
-        if (ch && strlen(ch) > 0) {
-            prefs_set_roster_header_char(ch[0]);
+        if (ch && g_utf8_strlen(ch, 4) == 1) {
+            prefs_set_roster_header_char(ch);
             g_free(ch);
         }
     }