Delete the variant-specific NullDisplayDriver.h and update target.h to use the shared implementation from #735

variants/heltec_t114/NullDisplayDriver.h

@@ -1,24 +0,0 @@
-#pragma once
-
-#include <helpers/ui/DisplayDriver.h>
-
-class NullDisplayDriver : public DisplayDriver {
-public:
-  NullDisplayDriver() : DisplayDriver(128, 64) { }
-  bool begin() { return false; }   // not present
-
-  bool isOn() override { return false; }
-  void turnOn() override { }
-  void turnOff() override { }
-  void clear() override { }
-  void startFrame(Color bkg = DARK) override { }
-  void setTextSize(int sz) override { }
-  void setColor(Color c) override { }
-  void setCursor(int x, int y) override { }
-  void print(const char* str) override { }
-  void fillRect(int x, int y, int w, int h) override { }
-  void drawRect(int x, int y, int w, int h) override { }
-  void drawXbm(int x, int y, const uint8_t* bits, int w, int h) override { }
-  uint16_t getTextWidth(const char* str) override { return 0; }
-  void endFrame() { }
-};

variants/heltec_t114/target.h

@@ -14,7 +14,7 @@
 #ifdef HELTEC_T114_WITH_DISPLAY
 #include <helpers/ui/ST7789Display.h>
 #else
-#include "NullDisplayDriver.h"
+#include "helpers/ui/NullDisplayDriver.h"
 #endif
 #endif