More Misc Sentry Fixes (#22496)

Sorting runtime errors by most events in the past 2 weeks, here's a few
fixes for the following:

https://aurorastation.sentry.io/issues/7472147004 - Runtime when someone
attempts to move before their character is placed in the world.

https://aurorastation.sentry.io/issues/7443212526 - Runtime when
harvesting plants

https://aurorastation.sentry.io/issues/7466716994 - Runtime when
vampires try to drink a bloodbag

https://aurorastation.sentry.io/issues/7496800530 - Runtime when a
player disconnects while a tgui window is open.

code/modules/mob/living/carbon/human/human_movement.dm

@@ -141,7 +141,7 @@
 		if(!footsound)
 			footsound = T.footstep_sound
 
-	if (client)
+	if (client && T)
 		var/turf/T1 = GET_TURF_ABOVE(T)
 		if(up_hint)
 			up_hint.icon_state = "uphint[(T1 ? !!isopenturf(T1) : 0)]"