fix: break sweep loop on frequency change

main.c

@@ -793,6 +793,8 @@ update_frequencies(void)
   }
 
   set_frequencies(start, stop, sweep_points);
+  operation_requested = OP_FREQCHANGE;
+  
   update_marker_index();
   
   // set grid layout

nanovna.h

@@ -86,6 +86,9 @@ extern int8_t sweep_enabled;
 extern void ui_init(void);
 extern void ui_process(void);
 
+enum { OP_NONE = 0, OP_LEVER, OP_TOUCH, OP_FREQCHANGE };
+extern uint8_t operation_requested;
+
 /*
  * dsp.c
  */

ui.c

@@ -59,7 +59,6 @@ static uint32_t last_button_down_ticks;
 static uint32_t last_button_repeat_ticks;
 static int8_t inhibit_until_release = FALSE;
 
-enum { OP_NONE = 0, OP_LEVER, OP_TOUCH };
 uint8_t operation_requested = OP_NONE;
 
 int8_t previous_marker = -1;