docs: use real Exception class in sample code

Author: kenjis

user_guide_src/source/general/errors.rst

@@ -41,7 +41,7 @@ Catching Specific Exceptions
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 In the example above, we catch any type of Exception. If we only want to watch for specific types of exceptions, like
-a ``UnknownFileException``, we can specify that in the catch parameter. Any other exceptions that are thrown and are
+a ``DataException``, we can specify that in the catch parameter. Any other exceptions that are thrown and are
 not child classes of the caught exception will be passed on to the error handler:
 
 .. literalinclude:: errors/003.php

user_guide_src/source/general/errors/003.php

@@ -1,7 +1,9 @@
 <?php
 
+use CodeIgniter\Database\Exceptions\DataException;
+
 try {
     $user = $userModel->find($id);
-} catch (\CodeIgniter\UnknownFileException $e) {
+} catch (DataException $e) {
     // do something here...
 }

user_guide_src/source/general/errors/004.php

@@ -1,8 +1,10 @@
 <?php
 
+use CodeIgniter\Database\Exceptions\DataException;
+
 try {
     $user = $userModel->find($id);
-} catch (\CodeIgniter\UnknownFileException $e) {
+} catch (DataException $e) {
     // do something here...
 
     throw new \RuntimeException($e->getMessage(), $e->getCode(), $e);