NPE in isPartner in world upgraded from 1.4.5

[Ellie .]

I get the following crash randomly when I have bees from extra bees in any gui screen (apiarist's chests, apiaries, my inventory, etc). I'm using 1.4.9.5. It doesn't happen consistently or immediately, but most of the time it will crash within one minute of opening an inventory as such.

2012-12-24 15:40:17 [INFO] [STDERR] t: Rendering screen
2012-12-24 15:40:17 [INFO] [STDERR]     at ban.b(EntityRenderer.java:1159)
2012-12-24 15:40:17 [INFO] [STDERR]     at net.minecraft.client.Minecraft.J(Minecraft.java:882)
2012-12-24 15:40:17 [INFO] [STDERR]     at net.minecraft.client.Minecraft.run(Minecraft.java:771)
2012-12-24 15:40:17 [INFO] [STDERR]     at java.lang.Thread.run(Unknown Source)
2012-12-24 15:40:17 [INFO] [STDERR] Caused by: java.lang.NullPointerException
2012-12-24 15:40:17 [INFO] [STDERR]     at binnie.extrabees.genetics.ExtraBeeMutation.isPartner(ExtraBeeMutation.java:631)
2012-12-24 15:40:17 [INFO] [STDERR]     at forestry.apiculture.genetics.BeeTemplates.getCombinations(BeeTemplates.java:105)
2012-12-24 15:40:17 [INFO] [STDERR]     at forestry.apiculture.gui.GuiApiaristInventory.displaySpeciesInformation(GuiApiaristInventory.java:189)
2012-12-24 15:40:17 [INFO] [STDERR]     at forestry.apiculture.gui.GuiApiaristInventory.drawGuiContainerBackgroundLayer(GuiApiaristInventory.java:78)
2012-12-24 15:40:17 [INFO] [STDERR]     at forestry.core.gui.GuiForestry.a(GuiForestry.java:231)
2012-12-24 15:40:17 [INFO] [STDERR]     at ban.b(EntityRenderer.java:1150)
2012-12-24 15:40:17 [INFO] [STDERR]     ... 3 more

This world has been using prerelease versions of Extra Bees and has been updated since 1.4.2, so I've used quite a few versions of Extra Bees in my world, which may be a contributing factor.

It appears to only be actual bees crashing it - stuff like the apiarist's database works fine, from what I can tell.

I'm using Forge 6.5.0.480, and Forestry 1.6.4.1.