fix: the null value check issue in image spacing calculation (#5726)

Co-authored-by: 顾争 <zheng.gu-rd@djhealthunion.com.cn>
Co-authored-by: Bill Wallace <wayfarer3130@gmail.com>

extensions/default/src/utils/validations/areAllImageSpacingEqual.ts

@@ -24,7 +24,9 @@ export default function areAllImageSpacingEqual(
     return;
   }
   const lastIpp = toNumber(instances[instances.length - 1].ImagePositionPatient);
-
+  if (!lastIpp) {
+    return;
+  }
   const averageSpacingBetweenFrames =
     _getPerpendicularDistance(firstImagePositionPatient, lastIpp) / (instances.length - 1);