Merge pull request #3867 from RosettaCommons/vmullig/fix_motifgraftmover
Fixing uninitialized variable error that's bothering gcc 8.2
The recent changes to the MotifGraftMover left gcc 8.2 complaining about an unintialized variable. Technically, the value would never be used uninitialized, but it would have been hard for the compiler to know that (and anyways, it was fragile -- a small change to the code would result in the variable being used uninitialized). This initializes the relevant variable.