Fixed member-call-on-null-pointer in getMember() when array is empty

CHANGELOG.md

@@ -15,6 +15,7 @@ HEAD
 * Changed `JsonVariantConst::is<JsonArray/JsonObject>()` to return `false` (issue #1412)
 * Simplified `JsonVariant::as<T>()` to always return `T` (see below)
 * Updated folders list in `.mbedignore` (PR #1515 by @AGlass0fMilk)
+* Fixed member-call-on-null-pointer in `getMember()` when array is empty
 
 > ### BREAKING CHANGES
 >

src/ArduinoJson/Collection/CollectionImpl.hpp

@@ -115,6 +115,8 @@ inline VariantSlot* CollectionData::getSlot(TAdaptedString key) const {
 }
 
 inline VariantSlot* CollectionData::getSlot(size_t index) const {
+  if (!_head)
+    return 0;
   return _head->next(index);
 }