Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
First of all the crashes aren't caused by the core dumps. Very basically a core dump is just the system dumping all the data that an application has in memory into a file AFTER an application has crashed. To help developers try to diagnose the cause of a crash. The error "Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again" is just telling you that it wasn't able to gather this data.

The actual crash in this case appears to have been caused by one of the mods you have installed. The important part of the crash report is these first few lines...

Description: WDL mod: exception in onWorldRemoveEntityFromWorld event

java.lang.null.NullPointerException: WDL mod: exception in onWorldRemoveEntityFromWorld event
                    at wdl.WDLHooks.onWorldRemoveEntityFromWorld(WDLHooks.java:153)
                    at wdl.litemod.LiteModWDL.worldClientRemoveEntityFromWorld(LiteModWDL.java:104)
                    at com.mumfrey.liteloader.core.event.EventProxy.$event0000d(EventProxy.java:224)


Unfortunately there isn't enough information here to tell us which mod.

First thing I'd recommend is making sure you have Minecraft and all your mods up to date. If that doesn't solve the problem, then I'd recommend removing each mod one by one and playing a bit each time. Then when the crashes stop you know which mod was the cause. Process of elimination.