added declaration of 'result_coefficient' and 'result_variables'

src/main/py/read_math_function.py

@@ -95,4 +95,6 @@ def simplify_exponential_function(type, function):
 def simplify_product_function(type, function):
     if type != "p":
         return False
-    terms = function.split('*')
+    terms = function.split('*')
+    result_coefficient = 1
+    result_variables = ""