Corrected unused var, default switch, Travis tests (#12477)

Marlin/src/HAL/shared/I2cEeprom.cpp

@@ -129,7 +129,6 @@ void eeprom_update_block(const void *pos, void* eeprom_address, size_t n) {
 
 
 uint8_t eeprom_read_byte(uint8_t *pos) {
-  byte data = 0xFF;
   unsigned eeprom_address = (unsigned)pos;
 
   eeprom_init();

Marlin/src/module/tool_change.cpp

@@ -479,6 +479,8 @@ inline void invalid_extruder_error(const uint8_t e) {
         active_extruder_parked = true;
         delayed_move_time = 0;
         break;
+      default:
+        break;
     }
 
     #if ENABLED(DEBUG_LEVELING_FEATURE)