lottieparser: Stop parsing if the media type is unlikely to lottie.

Users may need to try a load data in a brutal-force way,
if they have no idea of input source.

This case, they have no choices but try using all methods to find out
which loader successfully loaded among various media loaders.

This is a common scenario for compatible media support.

src/lottie/lottieparser.cpp

@@ -170,11 +170,9 @@ protected:
 class LottieParserImpl : public LookaheadParserHandler {
 public:
     LottieParserImpl(char *str, const char *dir_path)
-        : LookaheadParserHandler(str), mDirPath(dir_path)
-    {
-        ParseNext();
-    }
-    void ParseNext();
+        : LookaheadParserHandler(str), mDirPath(dir_path) {}
+    bool VerifyType();
+    bool ParseNext();
 public:
     bool        EnterObject();
     bool        EnterArray();
@@ -280,17 +278,26 @@ LookaheadParserHandler::LookaheadParserHandler(char *str)
     r_.IterativeParseInit();
 }
 
-void LottieParserImpl::ParseNext()
+bool LottieParserImpl::VerifyType()
+{
+    /* Verify the media type is lottie json.
+       Could add more strict check. */
+    return ParseNext();
+}
+
+bool LottieParserImpl::ParseNext()
 {
     if (r_.HasParseError()) {
         st_ = kError;
-        return;
+        return false;
     }
 
     if (!r_.IterativeParseNext<parseFlags>(ss_, *this)) {
         vCritical << "Lottie file parsing error";
-        RAPIDJSON_ASSERT(0);
+        st_ = kError;
+        return false;
     }
+    return true;
 }
 
 bool LottieParserImpl::EnterObject()
@@ -2244,7 +2251,10 @@ LottieParser::~LottieParser() = default;
 LottieParser::LottieParser(char *str, const char *dir_path)
     : d(std::make_unique<LottieParserImpl>(str, dir_path))
 {
-    d->parseComposition();
+    if (d->VerifyType())
+        d->parseComposition();
+    else
+        vWarning << "Input data is not Lottie format!";
 }
 
 std::shared_ptr<LOTModel> LottieParser::model()