Do not setTag to bottomTabs if testId is null (#4935)

Fixes #4812

lib/android/app/src/main/java/com/reactnativenavigation/presentation/BottomTabPresenter.java

             bottomTabs.setTitleInactiveColor(i, tab.textColor.get(null));
             bottomTabs.setTitleInactiveTextSizeInSp(i, tab.fontSize.hasValue() ? Float.valueOf(tab.fontSize.get()) : null);
             bottomTabs.setTitleActiveTextSizeInSp(i, tab.selectedFontSize.hasValue() ? Float.valueOf(tab.selectedFontSize.get()) : null);
-            bottomTabs.setTag(i, tab.testId.get(null));
+            if (tab.testId.hasValue()) bottomTabs.setTag(i, tab.testId.get());
         }
     }