Fix an assertion.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@118202 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/Frontend/FrontendAction.h b/include/clang/Frontend/FrontendAction.h
index 773543a..f659b2f 100644
--- a/include/clang/Frontend/FrontendAction.h
+++ b/include/clang/Frontend/FrontendAction.h
@@ -130,7 +130,7 @@
   }
 
   ASTUnit &getCurrentASTUnit() const {
-    assert(!CurrentASTUnit && "No current AST unit!");
+    assert(CurrentASTUnit && "No current AST unit!");
     return *CurrentASTUnit;
   }