Fix apct test.

Bug: 76208934
Test: atest incidentd_test
Change-Id: Ibc101aa3c523398b1e9dd6cff3d6735b4d704667
diff --git a/cmds/incidentd/src/Section.cpp b/cmds/incidentd/src/Section.cpp
index 5065a56..ece3083 100644
--- a/cmds/incidentd/src/Section.cpp
+++ b/cmds/incidentd/src/Section.cpp
@@ -374,9 +374,9 @@
     // ProtoOutputStream is to avoid allocation of another buffer inside ProtoOutputStream.
     EncodedBuffer* internalBuffer = buffer.getInternalBuffer();
     internalBuffer->writeHeader((uint32_t)GZippedFileProto::FILENAME, WIRE_TYPE_LENGTH_DELIMITED);
-    String8 usedFile(mFilenames[index]);
-    internalBuffer->writeRawVarint32(usedFile.size());
-    for (size_t i = 0; i < usedFile.size(); i++) {
+    size_t fileLen = strlen(mFilenames[index]);
+    internalBuffer->writeRawVarint32(fileLen);
+    for (size_t i = 0; i < fileLen; i++) {
         internalBuffer->writeRawByte(mFilenames[index][i]);
     }
     internalBuffer->writeHeader((uint32_t)GZippedFileProto::GZIPPED_DATA,