Removing code causing the trouble (#11898)

* Removing code causing the  trouble

Removing code that was apparently not needed in previous fix and caused regression 

Fixes: https://github.com/vaadin/framework/issues/11895

* Added feature to test UI

* Added test case

* Adding missing import

* Fixing test UI

* Enable DateField

client/src/main/java/com/vaadin/client/ui/VAbstractCalendarPanel.java

     public void renderCalendar(boolean updateDate) {
         if (parent instanceof VAbstractPopupCalendar
                 && !((VAbstractPopupCalendar) parent).popup.isShowing()) {
-            if (getDate() == null) {
-                // no date set, cannot pre-render yet
-                return;
-            }
             // a popup that isn't open cannot possibly need a focus change event
             updateDate = false;
         }

uitest/src/main/java/com/vaadin/tests/components/datefield/DateFieldMonthResolutionStatusChange.java

             dateField.setRangeEnd(LocalDate.of(2020, 1, 1));
         });
 
+        Button resetValueButton = new Button("Reset value");
+        resetValueButton.setId("resetValue");
+        resetValueButton.addClickListener(event -> {
+            dateField.setValue(LocalDate.now());
+        });
+
         addComponent(dateField);
         addComponent(dateReadOnlySwitch);
         addComponent(addRangeButton);
+        addComponent(resetValueButton);
     }
 
     @Override

uitest/src/test/java/com/vaadin/tests/components/datefield/DateFieldMonthResolutionStatusChangeTest.java

 import static org.junit.Assert.assertEquals;
 
 import org.junit.Test;
+import org.openqa.selenium.By;
 
 import com.vaadin.testbench.elements.ButtonElement;
 import com.vaadin.testbench.elements.DateFieldElement;
         assertEquals("Unexpected date change.", "1/19", df.getValue());
     }
 
+    @Test
+    public void testPopupOpenWithDateNotInRange() {
+        openTestURL();
+        DateFieldElement df = $(DateFieldElement.class).first();
+
+        // switch read-only state
+        $(ButtonElement.class).id("readOnly").click();
+        // set value before range
+        $(ButtonElement.class).id("resetValue").click();
+        // add range, previously set date is not in range
+        $(ButtonElement.class).id("addRange").click();
+
+        // Test that popup still opens
+        df.openPopup();
+        waitForElementPresent(By.className("v-datefield-popup"));
+        assertElementPresent(By.className("v-datefield-popup"));
+    }
+
 }