One more fix for #338, I really should get a heated bed to test with.

Marlin/temperature.cpp

@@ -1102,9 +1102,9 @@ ISR(TIMER0_COMPB_vect)
   /* No bed MINTEMP error? */
 #if defined(BED_MAXTEMP) && (TEMP_SENSOR_BED != 0)
 # if HEATER_BED_RAW_LO_TEMP > HEATER_BED_RAW_HI_TEMP
-    if(current_temperature_bed <= bed_maxttemp_raw) {
+    if(current_temperature_bed_raw <= bed_maxttemp_raw) {
 #else
-    if(current_temperature_bed >= bed_maxttemp_raw) {
+    if(current_temperature_bed_raw >= bed_maxttemp_raw) {
 #endif
        target_temperature_bed = 0;
        bed_max_temp_error();