Allow more fields in the case study to be blank

apps/map/models.py

@@ -477,6 +477,7 @@ class CaseStudy(models.Model):
         max_length=500,
         default=None,
         null=True,
+        blank=True
     )
 
     # 1.18.3
@@ -701,9 +702,9 @@ class CaseStudy(models.Model):
         help_text=_("Describe the size of concession(s) granted to company/companies (e.g. 'one concession encompassing\
                     2,300 hectares')"),
         max_length=200,
-        default=None,
         null=True,
-        blank=None
+        default=None,
+        blank=True
     )
 
     # 2.3.3.3
@@ -714,7 +715,7 @@ class CaseStudy(models.Model):
         max_length=256,
         default=None,
         null=True,
-        blank=None
+        blank=True
     )
 
     # 2.3.4