STR2783: make potential null string substituted to an empty string, still achieve internal cleanup in Fl_Text_Buffer::text(s)

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.3@9366 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

FL/Fl_Text_Buffer.H

@@ -188,7 +188,7 @@ public:
   
   /**  
    Replaces the entire contents of the text buffer.
-   \param text Text must be valid utf8.
+   \param text Text must be valid utf8. if null an empty string is substituted.
    */
   void text(const char* text);
   

src/Fl_Text_Buffer.cxx

@@ -165,7 +165,11 @@ char *Fl_Text_Buffer::text() const {
 void Fl_Text_Buffer::text(const char *t)
 {
   IS_UTF8_ALIGNED(t)
-  
+
+  // if t is null then substitute it with an empty string
+  // then don't return so that internal cleanup can happen
+  if (!t) t="";
+
   call_predelete_callbacks(0, length());
   
   /* Save information for redisplay, and get rid of the old buffer */