[Fix] Unable to open calendar view of the task (#3727)

frappe/desk/reportview.py

@@ -336,6 +336,9 @@ def build_match_conditions(doctype, as_condition=True):
 
 def get_filters_cond(doctype, filters, conditions, ignore_permissions=None, with_match_conditions=False):
 	if filters:
+		if isinstance(filters, basestring):
+			filters = json.loads(filters)
+
 		flt = filters
 		if isinstance(filters, dict):
 			filters = filters.items()