Fix projectExists check

Change equality check to work with "Optional" API. Using != null will
not lead to correct result as we need to check the object contained
inside Optional, not Optional itself. isPresent performs a check against
the object contained inside Optional and returns the correct and
desired value.

Bug: Issue 12454
Change-Id: I038e290b88b7599b8290735c96b16828f7f23b71

src/main/java/com/ericsson/gerrit/plugins/goimport/GoImportFilter.java

diff --git a/src/main/java/com/ericsson/gerrit/plugins/goimport/GoImportFilter.java b/src/main/java/com/ericsson/gerrit/plugins/goimport/GoImportFilter.java
index 93e4ba2..f59c9c1 100644
--- a/src/main/java/com/ericsson/gerrit/plugins/goimport/GoImportFilter.java
+++ b/src/main/java/com/ericsson/gerrit/plugins/goimport/GoImportFilter.java
@@ -194,6 +194,6 @@
 
   private boolean projectExists(String projectName) {
     Optional<ProjectState> p = projectCache.get(Project.nameKey(projectName));
-    return p != null;
+    return p.isPresent();
   }
 }