[Fix] Calender view broken if filters has not applied (#3737)

frappe/desk/reportview.py

@@ -335,10 +335,10 @@ def build_match_conditions(doctype, as_condition=True):
 		return match_conditions
 
 def get_filters_cond(doctype, filters, conditions, ignore_permissions=None, with_match_conditions=False):
-	if filters:
-		if isinstance(filters, basestring):
-			filters = json.loads(filters)
+	if isinstance(filters, basestring):
+		filters = json.loads(filters)
 
+	if filters:
 		flt = filters
 		if isinstance(filters, dict):
 			filters = filters.items()
@@ -363,4 +363,3 @@ def get_filters_cond(doctype, filters, conditions, ignore_permissions=None, with
 	else:
 		cond = ''
 	return cond
-