Fixed animation last key frame end time

Init keyframe end time with its start time, will be updated when parsing next key frame if any (solves issue interpolating to last keyframe) - Solves issue 548 Samsung#548

src/lottie/lottieparser.cpp

@@ -2032,6 +2032,7 @@ void LottieParserImpl::parseKeyFrame(model::KeyFrames<T, Tag> &obj)
             outTangent = parseInperpolatorPoint();
         } else if (0 == strcmp(key, "t")) {
             keyframe.start_ = GetDouble();
+            keyframe.end_ = keyframe.start_;
         } else if (0 == strcmp(key, "s")) {
             parsed.value = true;
             getValue(keyframe.value_.start_);