🐛 avoid assertion in patch (#5222)

docs/mkdocs/docs/api/basic_json/patch.md

@@ -32,6 +32,8 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
   could not be resolved successfully in the current JSON value; example: `"key baz not found"`.
 - Throws [`out_of_range.405`](../../home/exceptions.md#jsonexceptionout_of_range405) if JSON pointer has no parent
   ("add", "remove", "move")
+- Throws [`out_of_range.411`](../../home/exceptions.md#jsonexceptionout_of_range411) if an "add" operation's target
+  location has a parent that is neither an object nor an array.
 - Throws [`other_error.501`](../../home/exceptions.md#jsonexceptionother_error501) if "test" operation was
   unsuccessful.
 
@@ -71,3 +73,5 @@ is thrown. In any case, the original value is not changed: the patch is applied
 ## Version history
 
 - Added in version 2.0.0.
+- Added [`out_of_range.411`](../../home/exceptions.md#jsonexceptionout_of_range411) and stopped relying on an internal assertion when an "add" operation's
+  target location has a non-object/non-array parent in version 3.12.x.

docs/mkdocs/docs/api/basic_json/patch_inplace.md

@@ -28,6 +28,8 @@ No guarantees, value may be corrupted by an unsuccessful patch operation.
   could not be resolved successfully in the current JSON value; example: `"key baz not found"`.
 - Throws [`out_of_range.405`](../../home/exceptions.md#jsonexceptionout_of_range405) if JSON pointer has no parent
   ("add", "remove", "move")
+- Throws [`out_of_range.411`](../../home/exceptions.md#jsonexceptionout_of_range411) if an "add" operation's target
+  location has a parent that is neither an object nor an array.
 - Throws [`other_error.501`](../../home/exceptions.md#jsonexceptionother_error501) if "test" operation was
   unsuccessful.
 
@@ -68,3 +70,5 @@ function throws an exception.
 ## Version history
 
 - Added in version 3.11.0.
+- Added [`out_of_range.411`](../../home/exceptions.md#jsonexceptionout_of_range411) and stopped relying on an internal assertion when an "add" operation's
+  target location has a non-object/non-array parent in version 3.12.x.

docs/mkdocs/docs/home/exceptions.md

@@ -881,6 +881,20 @@ a JSON pointer exceeds the range of `size_type` (e.g., on 32-bit platforms).
     array index 18446744073709551616 exceeds size_type
     ```
 
+### json.exception.out_of_range.411
+
+A JSON Patch `add` operation cannot be applied because the target location's parent is neither an object nor an array. Per [RFC 6902](https://datatracker.ietf.org/doc/html/rfc6902), an `add` target must reference a member of an existing object or an element of an existing array; a primitive value (string, number, boolean, etc.) cannot receive a new member or element.
+
+!!! failure "Example message"
+
+    ```
+    cannot add value: the JSON Patch 'add' target's parent is of type string, but must be an object or array
+    ```
+
+!!! note
+
+    This exception was added in version 3.12.x. Before that, this situation hit an internal assertion (aborting the program in debug builds) or was silently ignored when assertions were disabled.
+
 ## Further exceptions
 
 This exception is thrown in case of errors that cannot be classified with the