add quotes

Author: vladak

opengrok-indexer/src/main/java/org/opengrok/indexer/search/Results.java

@@ -308,7 +308,7 @@ private static void printPlain(PrintPlainFinalArgs fargs, Document doc,
                     fargs.xrefPrefix, fargs.morePrefix, rpath, tags, true,
                     isDefSearch, null, scopes);
             } catch (IOException ex) {
-                String errMsg = String.format("No context for %s", sourceFile);
+                String errMsg = String.format("No context for '%s'", sourceFile);
                 if (LOGGER.isLoggable(Level.FINE)) {
                     // WARNING but with FINE detail
                     LOGGER.log(Level.WARNING, errMsg, ex);