[lldb] Change the statusline format to print "no target" (#139021)

Change the default statusline format to print "no target" when lldb is
launched without a target. Currently, the statusline is empty, which
looks rather odd.
diff --git a/lldb/source/Core/CoreProperties.td b/lldb/source/Core/CoreProperties.td
index 2498841..78988ce 100644
--- a/lldb/source/Core/CoreProperties.td
+++ b/lldb/source/Core/CoreProperties.td
@@ -186,7 +186,7 @@
       : Property<"statusline-format", "FormatEntity">,
         Global,
         DefaultStringValue<
-            "${ansi.negative}{${target.file.basename}}{ "
+            "${ansi.negative}{${target.file.basename}|no target}{ "
             "${separator}${line.file.basename}:${line.number}:${line.column}}{ "
             "${separator}${thread.stop-reason}}{ "
             "${separator}{${progress.count} }${progress.message}}">,