Workaround for bug nvaccess/nvda#17563 in NVDA 2025.1 alpha

It is also a minor speedup in that it no longer computes the braille string when there is no braille display.

Author: NSoiffer

addon/globalPlugins/MathCAT/MathCAT.py

@@ -298,6 +298,9 @@ def script_navigate(self, gesture: KeyboardInputGesture):
             # Translators: this message directs users to look in the log file
             speech.speakMessage(_("Error in navigating math: see NVDA error log for details"))
 
+        if not braille.handler.enabled:
+            return
+        
         try:
             # update the braille to reflect the nav position (might be excess code, but it works)
             nav_node = libmathcat.GetNavigationMathMLId()