No value for argument in options.txt not correctly parsed (Skipping bad option: lastServer:)

The bug

When you leave the "Direct Connect" field in the multiplayer menu empty your launcher will print the following warning on startup:

[Client thread/WARN]: Skipping bad option: lastServer:

The reason

The following is based on a decompiled version of Minecraft 1.10 using MCP 9.30.

The method net.minecraft.client.settings.GameSettings.loadOptions() calls on the splitter the method com.google.common.base.Splitter.omitEmptyStrings() this makes Strings like option: splitted at : become ["option"] instead of ["option",""].
Because of this options with empty String values become a list with one item only. However, the code following after that tries to get two items.

This could be fixed by leaving the call to the method com.google.common.base.Splitter.omitEmptyStrings() out.