guarded pdf meta data to require hyperref

src/config.tex

-% Meta Data for the PDF file using values from personal.tex:
-\hypersetup{
-	pdfinfo={
-		Title={\@title},
-		Author={\@author},
-		Subject={\@subject},
-		Keywords={\@keywords}
-	}
-}
-
 % abbreviations for names:
 \if@german
 	\renewcommand{\abstractname}{Abstract} % Abstract
@@ -25,6 +15,17 @@
 	%\setcapwidth[l]{0.8\textwidth} % leftalign all captions
 \fi
 
+% Meta Data for the PDF file using values from personal.tex:
+\@ifpackageloaded{hyperref}{
+	\hypersetup{
+		pdfinfo={
+			Title={\@title},
+			Author={\@author},
+			Subject={\@subject},
+			Keywords={\@keywords}
+		}
+	}
+}{}%
 % configs for optional packages:
 \@ifpackageloaded{biblatex}{
 	\ExecuteBibliographyOptions{