fix a few more src test errors

public/app/features/alerting/unified/components/rule-editor/notificaton-preview/NotificationPreview.tsx

@@ -140,7 +140,7 @@ export const NotificationPreview = ({
                   <div className={styles.firstAlertManagerLine} />
                   <div className={styles.alertManagerName}>
                     <Trans i18nKey="alerting.notification-preview.alertmanager">Alertmanager:</Trans>
-                    <img src={alertManagerSource.imgUrl} alt="" className={styles.img} />
+                    <img src={alertManagerSource.imgUrl || undefined} alt="" className={styles.img} />
                     {alertManagerSource.name}
                   </div>
                   <div className={styles.secondAlertManagerLine} />

public/app/features/datasources/components/picker/DataSourceLogo.tsx

@@ -20,7 +20,7 @@ export function DataSourceLogo(props: DataSourceLogoProps) {
     <img
       className={styles.pickerDSLogo}
       alt={`${dataSource.meta.name} logo`}
-      src={dataSource.meta.info.logos.small}
+      src={dataSource.meta.info.logos.small || undefined}
     ></img>
   );
 }

public/app/features/panel/components/VizTypePicker/PanelTypeCard.tsx

@@ -55,7 +55,11 @@ const PanelTypeCardComponent = ({
         isCurrent ? t('panel.panel-type-card.title-click-to-close', 'Click again to close this section') : plugin.name
       }
     >
-      <img className={cx(styles.img, { [styles.disabled]: isDisabled })} src={plugin.info.logos.small} alt="" />
+      <img
+        className={cx(styles.img, { [styles.disabled]: isDisabled })}
+        src={plugin.info.logos.small || undefined}
+        alt=""
+      />
 
       <div className={cx(styles.itemContent, { [styles.disabled]: isDisabled })}>
         <div className={styles.name}>{title}</div>