Tests/CheckLogFiles: Fix the test

We should only ignore the lines with {} and heartbeat messages from the
ZeroMQ XOP. And only if we only have these lines can we skip the file.

Added also two more info calls for better debugging.

Bug introduced in ed8a41d (LOG_AddEntry: Readd timestamp, 2023-12-11).

Packages/tests/Basic/UTF_Utils.ipf

@@ -7391,12 +7391,13 @@ End
 
 static Function CheckLogFiles()
 
+	string file, line
+	variable foundFiles, jsonID
+
 	// ensure that the ZeroMQ logfile exists as well
+	// and also have the right layout
 	PrepareForPublishTest()
 
-	string file
-	variable foundFiles, jsonID
-
 	WAVE/T filesAndOther = GetLogFileNames()
 	Duplicate/RMD=[][0]/FREE/T filesAndOther, files
 
@@ -7409,16 +7410,28 @@ static Function CheckLogFiles()
 		CHECK_WAVE(contents, TEXT_WAVE)
 		CHECK_GT_VAR(DimSize(contents, ROWS), 0)
 
-		if(!cmpstr(contents[0], "{}"))
+		for(line : contents)
+			if(cmpstr(line, "{}"))
+				break
+			endif
+		endfor
+
+		if(!cmpstr(line, "{}"))
+			// only {} inside the file, no need to check for timestamp
 			continue
 		endif
 
-		jsonID = JSON_Parse(contents[0])
+		jsonID = JSON_Parse(line)
 		CHECK(JSON_IsValid(jsonID))
 
+		INFO("File: \"%s\", Line: \"%s\"", s0 = file, s1 = line)
+
 		CHECK(MIES_LOG#LOG_HasRequiredKeys(jsonID))
 		WAVE/T keys = JSON_GetKeys(jsonID, "")
 		FindValue/TEXT="ts" keys
+
+		INFO("File: \"%s\", Line: \"%s\"", s0 = file, s1 = line)
+
 		CHECK_GE_VAR(V_Value, 0)
 
 		foundFiles += 1