Fix cmake error from CeresConfig.cmake when Ceres not found

Change-Id: I944c950ecfcb23d4c49b2b4f98852a99913f2f8b

cmake/CeresConfig.cmake.in

diff --git a/cmake/CeresConfig.cmake.in b/cmake/CeresConfig.cmake.in
index 14ab342..fa0697a 100644
--- a/cmake/CeresConfig.cmake.in
+++ b/cmake/CeresConfig.cmake.in
@@ -84,7 +84,7 @@
   # FindPackage() use the camelcase library name, not uppercase.
   if (Ceres_FIND_QUIETLY)
     message(STATUS "Failed to find Ceres - " ${REASON_MSG} ${ARGN})
-  else (Ceres_FIND_REQUIRED)
+  elseif (Ceres_FIND_REQUIRED)
     message(FATAL_ERROR "Failed to find Ceres - " ${REASON_MSG} ${ARGN})
   else()
     # Neither QUIETLY nor REQUIRED, use SEND_ERROR which emits an error