Fix unexpected growing of internal buffers up to max size when parsing from java.io.InputStream and java.nio.DirectByteBuffer

Author: plokhotnyuk

jsoniter-scala-core/js/src/main/scala/com/github/plokhotnyuk/jsoniter_scala/core/JsonReader.scala

@@ -4051,9 +4051,7 @@ final class JsonReader private[jsoniter_scala](
       if (mark > 0) mark = 0
       tail = remaining
       head = newPos
-    } else {
-      if (tail > 0) growBuf()
-    }
+    } else if (buf.length == tail) growBuf()
     var len = buf.length - tail
     if (bbuf ne null) {
       len = Math.min(bbuf.remaining, len)

jsoniter-scala-core/jvm-native/src/main/scala/com/github/plokhotnyuk/jsoniter_scala/core/JsonReader.scala

@@ -4506,9 +4506,7 @@ final class JsonReader private[jsoniter_scala](
       if (mark > 0) mark = 0
       tail = remaining
       head = newPos
-    } else {
-      if (tail > 0) growBuf()
-    }
+    } else if (buf.length == tail) growBuf()
     var len = buf.length - tail
     if (bbuf ne null) {
       len = Math.min(bbuf.remaining, len)