Move #2034 into 5.12.0 (#2036)

Author: paulb777

Firebase/Core/CHANGELOG.md

@@ -1,7 +1,7 @@
 # Unreleased
-- [fixed] Fixed static analysis warning for improper `nil` comparison. (#2034)
 
 # 2018-10-31 -- v5.1.7 -- M37
+- [fixed] Fixed static analysis warning for improper `nil` comparison. (#2034)
 - [changed] Assign the default app before posting notifications. (#2024)
 - [changed] Remove unnecessary notification flag. (#1993)
 - [changed] Wrap diagnostics notification in collection flag check. (#1979)