Static variable declaration causes unresolved external errors when calling FRootMotionMovementParams functions

Attempting to call a FRootMotionMovementParams function results in an unresolved externals error on compile because of the static FVector RootMotionScale variable.

Workaround:
In source, removing static allows code to compile successfully.

1. Open UE4 Editor (any project)
2. Add code to project based on Actor (MyActor)
3. Add the following to MyActor.cpp BeginPlay() function

   FRootMotionMovementParams MyParams;
   MyParams.ConsumeRootMotion(0.5f);
   

4. Compile

Result:
Compile fails with Unresolved External error shown in callstack field

Expected:
RootMotionMovementParams is recognized and code compiles.

LNK2001 unresolved external symbol "private: static struct FVector FRootMotionMovementParams::RootMotionScale" (?RootMotionScale@FRootMotionMovementParams@@0UFVector@@A)