Fix size-check parser

GitOrigin-RevId: 3bddd2fc299d54642739cc4e5b9e1a87027fc718

Author: stepankuzmin

build/check-ts-suppressions.ts

@@ -63,7 +63,11 @@ if (priorCommit) {
     if (!priorSummary) {
         console.warn(`No prior suppressions data found for check "${CHECK_NAME}" at ${priorCommit}, proceeding without comparison`);
     } else {
-        priorSuppressions = JSON.parse(priorSummary) as number;
+        try {
+            priorSuppressions = JSON.parse(priorSummary) as number;
+        } catch (_) {
+            console.warn(`Prior suppressions summary at ${priorCommit} is not JSON, proceeding without comparison`);
+        }
     }
 }