added assignment to simplified_term for simplify_product_function

src/main/py/read_math_function.py

@@ -102,3 +102,4 @@ def simplify_product_function(type, function):
         simplified_term = simplify_easy_math_function("v", term.strip())
         if not simplified_term or len(simplified_term) != 2:
             return False
+        term_coefficient, term_variables = simplified_term