Fixed a parser warning in classDiagram

Fixed a regression bug I introduced in theme.spec.js

cypress/integration/rendering/theme.spec.js

@@ -233,7 +233,9 @@ erDiagram
               Do work: 1: Me, Cat
             section Go home
               Go downstairs: 5: Me
-              Sit down: 5: Me          `
+              Sit down: 5: Me
+                        `,
+          {theme}
         );
         cy.get('svg');
     });

src/diagrams/class/parser/classDiagram.jison

@@ -147,8 +147,8 @@ mermaidDoc
 
 graphConfig
     : NEWLINE
-    | NEWLINE graphConfig
     | graphConfig NEWLINE
+    | NEWLINE CLASS_DIAGRAM NEWLINE statements EOF
     | CLASS_DIAGRAM NEWLINE statements EOF
     ;