Take care not to attempt copying the finish_installation.app unless we have actually succeeded in locating it. In the strange scenario that the finish_installation.app was not present in the Sparkle bundle, the target path was evaluated as being the host app's Application Support folder itself, and Sparkle would proceed to completely wipe out the host's Application Support folder as it tried to copy the non-existent
Quiet a warning caused by using a non-constant template format string.