text: Title: JMA indicator ValueError: cannot convert float NaN to integer
  Body: pandas-ta: 0.3.14b0
  
  Running `df.ta.strategy()` or more specifically `df.ta.jma()` on a simple dataframe fails with
  
  ```sh
  Error
  Traceback (most recent call last):
    File "/Users/andrei/Projects/BE/breakingequity/breakingequity-backtest-single-day/tests/test_ohlcdata.py", line 60, in test_jma
      df.ta.jma()
    File "/Users/andrei/.local/share/virtualenvs/breakingequity-backtest-single-day-Vn0CDZ8S/lib/python3.9/site-packages/pandas_ta/core.py", line 1199, in jma
      result = jma(close=close, length=length, phase=phase, offset=offset, **kwargs)
    File "/Users/andrei/.local/share/virtualenvs/breakingequity-backtest-single-day-Vn0CDZ8S/lib/python3.9/site-packages/pandas_ta/overlap/jma.py", line 76, in jma
      jma[0:_length - 1] = npNaN
  ValueError: cannot convert float NaN to integer
  ```
  
  Sample unit test:
  ```python
      def test_jma(self):
          minutes_range = pd.date_range(
              start=pd.Timestamp('2020-01-02 09:30:00-05:00'),
              end=pd.Timestamp('2020-01-02 16:00:00-05:00'),
              freq='1min')
          minutes = 390
  
          ohlc = [
              [1, 2, 1, 2, 10, 1.5],
              [2, 4, 2, 4, 20, 3.0],
              [3, 4, 3, 4, 20, 3.0],
          ]
          df = pd.DataFrame(
              ohlc * int(minutes / len(ohlc)),
              columns=['open', 'high', 'low', 'close', 'volume', 'vwap'],
              index=minutes_range[0:minutes]
          )
  
          df.ta.jma()
  ```
  
  