RVRNEXT-28 add further checks before manupulating db

src/Controller/CommunityController.php

@@ -199,7 +199,19 @@ class CommunityController implements IAuthenticationRequired
                 ]);
             }
         } else {
+            if ($this->transactionRepository->isAnyCommon()) {
+                return new JsonContent([
+                    'error' => ['errorText' => 'There are transactions with common payee!']
+                ]);
+            }
+
             $user = $this->userRepository->getById(\Container::$request->post('user_id'));
+            if ($this->communityMemberRepository->getByCommunityAndUser($community, $user) !== null) {
+                return new JsonContent([
+                    'error' => ['errorText' => 'This user is already a member of this community.']
+                ]);
+            }
+
             $communityMember = new CommunityMember();
             $communityMember->setCommunity($community);
             $communityMember->setUser($user);
@@ -295,6 +307,16 @@ class CommunityController implements IAuthenticationRequired
             return null;
         }
 
+        if ($this->transactionRepository->isAnyForCurrency($currency)) {
+            return new JsonContent([
+                'error' => ['errorText' => 'There are transactions with this currency!']
+            ]);
+        }
+
+        foreach ($this->currencyExchangeRatesRepository->getAllByCurrency($currency) as $currencyExchangeRate) {
+            \Container::$persistentDataManager->deleteFromDb($currencyExchangeRate);
+        }
+
         \Container::$persistentDataManager->deleteFromDb($currency);
 
         return new JsonContent(['success' => true]);