🐛 Fix FTDI Eve unicode and spinner dialog (#22459)

Marlin/src/lcd/extui/ftdi_eve_touch_ui/ftdi_eve_lib/extended/unicode/unicode.cpp

 
   utf8_char_t FTDI::get_utf8_char_and_inc(const char *&c) {
     utf8_char_t val = *(uint8_t*)c++;
-    while ((*c & 0xC0) == 0x80)
-      val = (val << 8) | *(uint8_t*)c++;
+    if ((val & 0xC0) == 0x80)
+      while ((*c & 0xC0) == 0x80)
+        val = (val << 8) | *(uint8_t*)c++;
     return val;
   }
 
   utf8_char_t FTDI::get_utf8_char_and_inc(char *&c) {
     utf8_char_t val = *(uint8_t*)c++;
-    while ((*c & 0xC0) == 0x80)
-      val = (val << 8) | *(uint8_t*)c++;
+    if ((val & 0xC0) == 0x80)
+      while ((*c & 0xC0) == 0x80)
+        val = (val << 8) | *(uint8_t*)c++;
     return val;
   }
 

Marlin/src/lcd/extui/ftdi_eve_touch_ui/generic/spinner_dialog_box.cpp

 
 constexpr static SpinnerDialogBoxData &mydata = screen_data.SpinnerDialogBox;
 
+void SpinnerDialogBox::onEntry() {
+  mydata.auto_hide = true;
+}
+
 void SpinnerDialogBox::onRedraw(draw_mode_t) {
 }
 
   drawMessage(message);
   drawSpinner();
   storeBackground();
+  GOTO_SCREEN(SpinnerDialogBox);
   mydata.auto_hide = false;
 }
 
 
 void SpinnerDialogBox::enqueueAndWait(progmem_str message, progmem_str commands) {
   show(message);
-  GOTO_SCREEN(SpinnerDialogBox);
   ExtUI::injectCommands_P((const char*)commands);
-  mydata.auto_hide = true;
 }
 
 void SpinnerDialogBox::enqueueAndWait(progmem_str message, char *commands) {
   show(message);
-  GOTO_SCREEN(SpinnerDialogBox);
   ExtUI::injectCommands(commands);
-  mydata.auto_hide = true;
 }
 
 void SpinnerDialogBox::onIdle() {

Marlin/src/lcd/extui/ftdi_eve_touch_ui/generic/spinner_dialog_box.h

 
 class SpinnerDialogBox : public DialogBoxBaseClass, public CachedScreen<SPINNER_CACHE,SPINNER_DL_SIZE> {
   public:
+    static void onEntry();
     static void onRedraw(draw_mode_t);
     static void onIdle();