Fix 'FileExistsError' shared memory exception (#945)

frigate/app.py

@@ -180,14 +180,23 @@ class FrigateApp:
         model_shape = (self.config.model.height, self.config.model.width)
         for name in self.config.cameras.keys():
             self.detection_out_events[name] = mp.Event()
-            shm_in = mp.shared_memory.SharedMemory(
-                name=name,
-                create=True,
-                size=self.config.model.height * self.config.model.width * 3,
-            )
-            shm_out = mp.shared_memory.SharedMemory(
-                name=f"out-{name}", create=True, size=20 * 6 * 4
-            )
+
+            try:
+                shm_in = mp.shared_memory.SharedMemory(
+                    name=name, 
+                    create=True, 
+                    size=self.config.model.height*self.config.model.width * 3,
+                )
+            except FileExistsError:
+                shm_in = mp.shared_memory.SharedMemory(name=name)
+
+            try:
+                shm_out = mp.shared_memory.SharedMemory(
+                    name=f"out-{name}", create=True, size=20 * 6 * 4
+                )
+            except FileExistsError:
+                shm_out = mp.shared_memory.SharedMemory(name=f"out-{name}")
+
             self.detection_shms.append(shm_in)
             self.detection_shms.append(shm_out)