[MC-148893] Fox spawners do not render the fox inside of the block

The bug

Foxes do not show up inside of spawner blocks. Although they do spawn from the spawner block.

Example

Here is an example:

Logs

The following error is printed in the log:

[Render thread/WARN]: Exception loading entity: 
q: Loading entity NBT at akn.f(SourceFile:1596) ~[1.15.1-pre1.jar:?] 
at akr.a(SourceFile:436) ~[1.15.1-pre1.jar:?] 
at akr$$Lambda$3010/38205588.accept(Unknown Source) ~[?:?] 
at t.a(SourceFile:341) ~[1.15.1-pre1.jar:?] 
at akr.a(SourceFile:435) ~[1.15.1-pre1.jar:?] 
at akr.b(SourceFile:488) [1.15.1-pre1.jar:?] 
at akr.a(SourceFile:469) [1.15.1-pre1.jar:?] 
at bja.d(SourceFile:256) [1.15.1-pre1.jar:?] 
at dsz.a(SourceFile:22) [1.15.1-pre1.jar:?] 
at dsz.a(SourceFile:12) [1.15.1-pre1.jar:?] 
at dsn.a(SourceFile:106) [1.15.1-pre1.jar:?] 
at dsn.b(SourceFile:95) [1.15.1-pre1.jar:?] 
at dsn$$Lambda$3606/1161820020.run(Unknown Source) [1.15.1-pre1.jar:?] 
at dsn.a(SourceFile:127) [1.15.1-pre1.jar:?] 
at dsn.a(SourceFile:95) [1.15.1-pre1.jar:?] 
at dqo.a(SourceFile:1207) [1.15.1-pre1.jar:?] 
at dqk.a(SourceFile:718) [1.15.1-pre1.jar:?] 
at dqk.a(SourceFile:543) [1.15.1-pre1.jar:?] 
at dbl.d(SourceFile:947) [1.15.1-pre1.jar:?] 
at dbl.b(SourceFile:585) [1.15.1-pre1.jar:?] 
at net.minecraft.client.main.Main.main(SourceFile:202) [1.15.1-pre1.jar:?]
Caused by: java.lang.NullPointerException 
at aqs.hashCode(SourceFile:93) ~[1.15.1-pre1.jar:?] 
at java.util.HashMap.hash(HashMap.java:338) ~[?:1.8.0_51] 
at java.util.HashMap.put(HashMap.java:611) ~[?:1.8.0_51] 
at java.util.HashSet.add(HashSet.java:219) ~[?:1.8.0_51] 
at ape.a(SourceFile:44) ~[1.15.1-pre1.jar:?] 
at ath.eD(SourceFile:370) ~[1.15.1-pre1.jar:?] 
at ath.a(SourceFile:448) ~[1.15.1-pre1.jar:?] 
at akn.f(SourceFile:1587) ~[1.15.1-pre1.jar:?] 
... 20 more