BUG: MACD with signalperiod = 1 - data leak

Hello everyone, I've encountered dangerous behavior of library while calculating MACD with signalperiod = 1: How to reproduce: ```python np.random.seed(42) test_data = np.random.randn(2000) * 100 + 1000 fastperiod = 2 slowperiod = 32 signalperiod = 1 macd_1, macdsignal_1, macdhist_1 = ta.MACD( real=np.append(test_data[:1500],-999999999), fastperiod=fastperiod, slowperiod=slowperiod, signalperiod=signalperiod ) macd_2, macdsignal_2, macdhist_2 = ta.MACD( real=test_data[:1501], fastperiod=fastperiod, slowperiod=slowperiod, signalperiod=signalperiod ) print(macdsignal_2[-3] - macdsignal_1[-3]) # Equals 606061258.6885501 ``` As I am checking [-3] index in the array - it shouldn't know about the upcoming value in the end, but the calculated delta shows that TA-Lib takes this value into account. Also I checked the correct parameters: ```python np.random.seed(42) test_data = np.random.randn(2000) * 100 + 1000 fastperiod = 2 slowperiod = 32 signalperiod = 2 macd_1, macdsignal_1, macdhist_1 = ta.MACD( real=np.append(test_data[:1500],-999999999), fastperiod=fastperiod, slowperiod=slowperiod, signalperiod=signalperiod ) macd_2, macdsignal_2, macdhist_2 = ta.MACD( real=test_data[:1501], fastperiod=fastperiod, slowperiod=slowperiod, signalperiod=signalperiod ) print(macdsignal_2[-3] - macdsignal_1[-3]) # Equals 0.0 ``` I think it is needed either to forbid signalperiod = 1 or to manually fill the macdhist array with zeros in this edge case.