Fix build errors and add a bit of failsafe

src/main.cpp

@@ -152,12 +152,11 @@ void setup()
     DEBUG_MSG("\n\n//\\ E S H T /\\ S T / C\n\n");
 
     initDeepSleep();
-    
-    #if defined(TTGO_T_ECHO)
-    DEBUG_MSG("\n\nTTGO_T_ECHO PIN_EINK_PWR_ON\n\n");
+
+    // Testing this fix für erratic T-Echo boot behaviour    
+#if defined(TTGO_T_ECHO) && defined(PIN_EINK_PWR_ON)
     pinMode(PIN_EINK_PWR_ON, OUTPUT);
     digitalWrite(PIN_EINK_PWR_ON, HIGH);
-#elif
 #endif
 
 #ifdef VEXT_ENABLE