Fix pdf content importer exception if DOI is empty

CHANGELOG.md

@@ -79,6 +79,7 @@ Note that this project **does not** adhere to [Semantic Versioning](http://semve
 - We fixed an issue where the context menu was not updated after a file link was changed. [#5777](https://github.com/JabRef/jabref/issues/5777)
 - We fixed an issue where the password for a shared SQL database was not remembered [#6869](https://github.com/JabRef/jabref/issues/6869)
 - We fixed an issue where newly added entires were not synced to a shared SQL database [#7176](https://github.com/JabRef/jabref/issues/7176)
+- We fixed an issue where the PDF-Content importer threw an exception when no DOI number is present at the first page of the PDF document [#7203](https://github.com/JabRef/jabref/issues/7203)
 
 ### Removed
 

src/main/java/org/jabref/logic/importer/fileformat/PdfContentImporter.java

@@ -418,15 +418,17 @@ Optional<BibEntry> getEntryFromPDFContent(String firstpageContents, String lineS
                     }
                     if (pos >= 0) {
                         pos += 3;
-                        char delimiter = curString.charAt(pos);
-                        if ((delimiter == ':') || (delimiter == ' ')) {
-                            pos++;
-                        }
-                        int nextSpace = curString.indexOf(' ', pos);
-                        if (nextSpace > 0) {
-                            DOI = curString.substring(pos, nextSpace);
-                        } else {
-                            DOI = curString.substring(pos);
+                        if (curString.length() > pos) {
+                            char delimiter = curString.charAt(pos);
+                            if ((delimiter == ':') || (delimiter == ' ')) {
+                                pos++;
+                            }
+                            int nextSpace = curString.indexOf(' ', pos);
+                            if (nextSpace > 0) {
+                                DOI = curString.substring(pos, nextSpace);
+                            } else {
+                                DOI = curString.substring(pos);
+                            }
                         }
                     }
                 }

src/test/java/org/jabref/logic/importer/fileformat/PdfContentImporterTest.java

@@ -88,4 +88,26 @@ void testParsingEditorWithoutPagesorSeriesInformation() {
 
         assertEquals(Optional.of(entry), importer.getEntryFromPDFContent(firstPageContents, "\n"));
     }
+
+    @Test
+    void testParsingWithoutActualDOINumber() {
+        BibEntry entry = new BibEntry(StandardEntryType.InProceedings);
+        entry.withField(StandardField.AUTHOR, "Link to record in KAR and http://kar.kent.ac.uk/51043/  and Document Version and UNSPECIFIED  and Master of Research (MRes) thesis and University of Kent")
+             .withField(StandardField.TITLE, "Kent Academic Repository Full text document (pdf) Citation for published version Smith, Lucy Anna (2014) Mortality in the Ornamental Fish Retail Sector: an Analysis of Stock Losses and Stakeholder Opinions. DOI")
+             .withField(StandardField.YEAR, "5104");
+
+        String firstPageContents = "Kent Academic Repository Full text document (pdf)\n"
+                                   + "Citation for published version\n"
+                                   + "Smith, Lucy Anna (2014) Mortality in the Ornamental Fish Retail Sector: an Analysis of Stock\n"
+                                   + "Losses and Stakeholder Opinions.\n"
+                                   + "DOI\n\n\n"
+                                   + "Link to record in KAR\n"
+                                   + "http://kar.kent.ac.uk/51043/\n"
+                                   + "Document Version\n"
+                                   + "UNSPECIFIED\n"
+                                   + "Master of Research (MRes) thesis, University of Kent,.";
+
+        assertEquals(Optional.of(entry), importer.getEntryFromPDFContent(firstPageContents, "\n"));
+
+    }
 }