Run SDM in strict mode to easier catch silly mistakes (#13567)

Change-Id: I6739260499e66245eff2b05bfeb84c430ef5ca19

eclipse/Super Development Mode (vaadin).launch

@@ -21,7 +21,7 @@
 </listAttribute>
 <booleanAttribute key="org.eclipse.jdt.launching.DEFAULT_CLASSPATH" value="false"/>
 <stringAttribute key="org.eclipse.jdt.launching.MAIN_TYPE" value="com.google.gwt.dev.codeserver.CodeServer"/>
-<stringAttribute key="org.eclipse.jdt.launching.PROGRAM_ARGUMENTS" value="-noprecompile -bindAddress 0.0.0.0 com.vaadin.DefaultWidgetSet  com.vaadin.tests.widgetset.TestingWidgetSet"/>
+<stringAttribute key="org.eclipse.jdt.launching.PROGRAM_ARGUMENTS" value="-noprecompile -strict -bindAddress 0.0.0.0 com.vaadin.DefaultWidgetSet  com.vaadin.tests.widgetset.TestingWidgetSet"/>
 <stringAttribute key="org.eclipse.jdt.launching.PROJECT_ATTR" value="vaadin"/>
 <stringAttribute key="org.eclipse.jdt.launching.VM_ARGUMENTS" value="-Xmx512M -XX:MaxPermSize=256M"/>
 </launchConfiguration>