Notice Fixes on Contribution Reports

Following notice Fixes on Contribution Reports namely "Contributions by Organization" and " Contribution Aggregate by Relationship"
--------------------------------------------------------------------------------------------------------------------------------------
Strict warning: Only variables should be assigned by reference in CRM_Report_Form_Contribute_OrganizationSummary->validRelationships() (line 390 of /home/web/src/civicrm/CRM/Report/Form/Contribute/OrganizationSummary.php).
Strict warning: Only variables should be assigned by reference in CRM_Report_Form_Contribute_OrganizationSummary->validRelationships() (line 399 of /home/web/src/civicrm/CRM/Report/Form/Contribute/OrganizationSummary.php).
Notice: Undefined index: 4_b_a in CRM_Report_Form_Contribute_OrganizationSummary->statistics() (line 355 of /home/web/src/civicrm/CRM/Report/Form/Contribute/OrganizationSummary.php).

Strict warning: Declaration of CRM_Report_Form_Contribute_History::buildRows() should be compatible with CRM_Report_Form::buildRows($sql, &$rows) in require_once() (line 36 of /home/web/src/civicrm/CRM/Report/Form/Contribute/History.php).