[IMP] mis_builder: change precision rounding from 2 to 4 to distinguish 0 from null in initial balances

This should be slightly on the safer side. Ideally, this rounding precision
should come from the kpi style (which defaults to the report style), but
that would be a lot of code for little benefits.

mis_builder/models/aep.py

@@ -266,7 +266,7 @@ class AccountingExpressionProcessor(object):
                 debit = acc['debit'] or 0.0
                 credit = acc['credit'] or 0.0
                 if mode in (self.MODE_INITIAL, self.MODE_UNALLOCATED) and \
-                        float_is_zero(debit-credit, precision_rounding=2):
+                        float_is_zero(debit-credit, precision_rounding=4):
                     # in initial mode, ignore accounts with 0 balance
                     continue
                 self._data[key][acc['account_id'][0]] = (debit, credit)
@@ -311,7 +311,7 @@ class AccountingExpressionProcessor(object):
             # as it does not make sense to distinguish 0 from "no data"
             if v is not AccountingNone and \
                     mode in (self.MODE_INITIAL, self.MODE_UNALLOCATED) and \
-                    float_is_zero(v, precision_rounding=2):
+                    float_is_zero(v, precision_rounding=4):
                 v = AccountingNone
             return '(' + repr(v) + ')'
 
@@ -342,7 +342,7 @@ class AccountingExpressionProcessor(object):
             # as it does not make sense to distinguish 0 from "no data"
             if v is not AccountingNone and \
                     mode in (self.MODE_INITIAL, self.MODE_UNALLOCATED) and \
-                    float_is_zero(v, precision_rounding=2):
+                    float_is_zero(v, precision_rounding=4):
                 v = AccountingNone
             return '(' + repr(v) + ')'