[lcd] forbid writing outside of current framebuffer memory

Core/Src/lcd.c

@@ -136,6 +136,12 @@ static void display_write_data_byte_direct(uint8_t code)
 
 static void display_write_data_byte_framebuffer(uint8_t code)
 {
+	if (display_current_frame >= DISPLAY_FRAMES_AVAILABLE)
+		return;
+
+	if (((int) des.cursor_offset >= 32) || ((int) des.cursor_offset < 0))
+		return;
+
 	display_framebuffer[16*2*display_current_frame + des.cursor_offset] = (char) code;
 	des.cursor_offset += des.next ? -1 : 1;
 }