matrix-synapse: Ensure there's a valid /tmp dir

charts/matrix-synapse/templates/deployment.yaml

@@ -143,6 +143,8 @@ spec:
               mountPath: /synapse/keys
             - name: media
               mountPath: /synapse/data
+            - name: tmpdir
+              mountPath: /tmp
           {{- with .Values.synapse.extraVolumeMounts }}
             {{- . | toYaml | nindent 12 }}
           {{- end }}
@@ -167,6 +169,8 @@ spec:
                 path: signing.key
         - name: tmpconf
           emptyDir: {}
+        - name: tmpdir
+          emptyDir: {}
         - name: media
         {{- $mediaworker := false }}
         {{- range $worker, $config := .Values.workers }}