Fix bug in calling __createReaction function when productStructures is None
Fix bug in calling __createReaction function when productStructures is None

This if statement must have been missed since it is present in every
other case in the code.

nyee/RMG-Py,enochd/RMG-Py,chatelak/RMG-Py,nickvandewiele/RMG-Py,nickvandewiele/RMG-Py,enochd/RMG-Py,comocheng/RMG-Py,nyee/RMG-Py,chatelak/RMG-Py,comocheng/RMG-Py,pierrelb/RMG-Py,pierrelb/RMG-Py