[Doc] Add new -display-{mode} method to manpage.

doc/rofi.1

@@ -1151,6 +1151,22 @@ Make \fBrofi\fP create a pid file and check this on startup. The pid file preven
 .PP
 Set the name to use for mode. This is used as prompt and in combi\-browser.
 
+.PP
+It is now prefered to use the configuration file:
+
+.PP
+.RS
+
+.nf
+configuration {
+  {mode} {
+    display\-name: *string*;
+  }
+}
+
+.fi
+.RE
+
 .PP
 \fB\fC\-click\-to\-exit\fR
 \fB\fC\-no\-click\-to\-exit\fR

doc/rofi.1.markdown

@@ -724,6 +724,17 @@ Make **rofi** create a pid file and check this on startup. The pid file prevents
 
 Set the name to use for mode. This is used as prompt and in combi-browser.
 
+It is now prefered to use the configuration file:
+
+```css
+configuration {
+  {mode} {
+    display-name: *string*;
+  }
+}
+```
+
+
 `-click-to-exit`
 `-no-click-to-exit`
 

source/mode.c

@@ -153,10 +153,12 @@ void mode_set_private_data ( Mode *mode, void *pd )
 
 const char *mode_get_display_name ( const Mode *mode )
 {
+  /** Find the widget */
   ThemeWidget *wid = rofi_config_find_widget ( mode->name, NULL, TRUE );
   if ( wid ) {
+    /** Check string property */
     Property    *p   = rofi_theme_find_property ( wid, P_STRING, "display-name", FALSE );
-    if ( p != NULL ) {
+    if ( p != NULL && p->type == P_STRING ) {
       return p->value.s;
     }
   }