BLF: String length to cursor position, not INT_MAX

BLF_str_offset_from_cursor_position is being called with a str_len of
INT_MAX, so max buffer size instead of string length. This works fine
right now but will not when this gets more complex. For example if we
need to call functions like BLI_str_cursor_step_next_utf8, which
assumes that str_len is the actual end of the string.

Pull Request: https://projects.blender.org/blender/blender/pulls/121966

source/blender/editors/interface/interface_handlers.cc

@@ -3114,8 +3114,9 @@ static void ui_textedit_set_cursor_pos(uiBut *but, uiHandleButtonData *data, con
   }
   /* mouse inside the widget, mouse coords mapped in widget space */
   else {
-    but->pos = but->ofs + BLF_str_offset_from_cursor_position(
-                              fstyle.uifont_id, str + but->ofs, INT_MAX, int(x - startx));
+    but->pos = but->ofs +
+               BLF_str_offset_from_cursor_position(
+                   fstyle.uifont_id, str + but->ofs, strlen(str + but->ofs), int(x - startx));
   }
 
   ui_but_text_password_hide(password_str, but, true);