fix bytearray:insert (#594)

dev/tests/bytearray.lua

@@ -28,3 +28,9 @@ assert(#arr == arr:get_capacity())
 
 arr = Bytearray({0, 2, 7, 1, 16, 75, 25})
 assert(arr[6] == 75)
+
+arr:insert(2, {5, 6})
+
+assert(arr[#arr] == 25)
+assert(arr[2] == 5)
+assert(arr[3] == 6)

res/modules/internal/bytearray.lua

@@ -71,7 +71,7 @@ local function insert(self, index, b)
     if self.size + elems > self.capacity then
         grow_buffer(self, elems)
     end
-    for i=self.size, index - 1, -1 do
+    for i = self.size - 1, index - 1, -1 do
         self.bytes[i + elems] = self.bytes[i]
     end
     if _type(b) == "number" then