🐛 Validate pin existence before adding image and improve error handling

app/routes/images.py

@@ -131,6 +131,10 @@ async def add_image(
         else:
             os.remove(temp_path)
         
+        if not pin_id == 'null':
+            if(pins_collection.find_one({"_id": ObjectId(pin_id)}) is None):
+                raise HTTPException(status_code=404, detail="Pin not found")
+        
         # Créer l'entrée en base de données
         image_doc = {
             "pin_id": ObjectId(pin_id) if pin_id != 'null' else None,
@@ -148,8 +152,8 @@ async def add_image(
         
         return {"id": str(image_id)}
         
-    except Exception as e:
-        # Nettoyer en cas d'erreur
+    except (OSError, IOError) as e:
+        # Nettoyer en cas d'erreur liée au système de fichiers
         if os.path.exists(temp_path):
             os.remove(temp_path)
         raise HTTPException(status_code=500, detail=str(e))
@@ -213,7 +217,7 @@ async def update_caption(
 )
 async def get_caption(id: str, current_user: User = Depends(get_current_user)):
     image = check_image_permissions(id, current_user)
-    return ImageCaptionDTO(caption=image.get("caption", ""))
+    return ImageCaptionDTO(caption=image.get("caption", " "))
 
 @images_router.get(
     path="/{id}/metadata",