Fix PepDB NPE from the crawler

[labkey-jeckels]

Rationale

ERROR PepDBController          2025-04-02T03:40:54,317     http-nio-8111-exec-1 : PeptideTextExportAction: 
java.lang.NullPointerException: Cannot invoke "java.lang.CharSequence.length()" because "this.text" is null
	at java.base/java.util.regex.Matcher.getTextLength(Matcher.java:1769) ~[?:?]
	at java.base/java.util.regex.Matcher.reset(Matcher.java:415) ~[?:?]
	at java.base/java.util.regex.Matcher.<init>(Matcher.java:252) ~[?:?]
	at java.base/java.util.regex.Pattern.matcher(Pattern.java:1134) ~[?:?]
	at org.labkey.api.data.TSVWriter.setFilenamePrefix(TSVWriter.java:109) ~[api-25.4-SNAPSHOT.jar:?]
	at org.scharp.atlas.pepdb.PepDBController$PeptideTextExportAction.printText(PepDBController.java:925) [pepdb-25.4-SNAPSHOT.jar:?]
	at org.scharp.atlas.pepdb.PepDBController$PeptideDefaultTextExportAction.export(PepDBController.java:973) [pepdb-25.4-SNAPSHOT.jar:?]
	at org.labkey.api.action.ExportAction.getView(ExportAction.java:52) [api-25.4-SNAPSHOT.jar:?]
	at org.labkey.api.action.SimpleViewAction.handleRequest(SimpleViewAction.java:75) [api-25.4-SNAPSHOT.jar:?]

Changes

• Use a default value for export filename
• Simplify exception handling a little more

[labkey-adam]

Thanks!