[MaterialCardView] Fixed NPE if android:onClick is defined in the layout

Resolves #1054
Resolves #1614

GIT_ORIGIN_REV_ID=b19044de3093f19313e362d378f5cc3b810c5727
PiperOrigin-RevId: 326486876

(cherry picked from commit 1b0cfae)

Author: wcshi

lib/java/com/google/android/material/card/MaterialCardView.java

@@ -312,7 +312,9 @@ public ColorStateList getCardForegroundColor() {
   @Override
   public void setClickable(boolean clickable) {
     super.setClickable(clickable);
-    cardViewHelper.updateClickable();
+    if (cardViewHelper != null){
+      cardViewHelper.updateClickable();
+    }
   }
 
   @Override