fix: call api pass chinese will cause error csd-71388 (#867)

Author: guoxianzhe

ios/AgoraRtcNg.mm

@@ -168,10 +168,13 @@ - (void)dealloc {
     char result[kBasicResultLength] = "";
     int error_code;
 
+    NSUInteger paramsLength =
+        [params lengthOfBytesUsingEncoding:NSUTF8StringEncoding];
+
     ApiParam param = {
         .event = funcName.UTF8String,
         .data = params.UTF8String,
-        .data_size = static_cast<unsigned int>(params.length),
+        .data_size = static_cast<unsigned int>(paramsLength),
         .result = result,
         .buffer = buffers,
         .length = length,