custombib with error catcher

Classes/PhDThesisPSnPDF.cls

@@ -365,28 +365,42 @@ supported!}
         \ClassWarning{PhDThesisPSnPDF}{Bibliography has already been loaded.
           Check document class options.}
       \else      % Load Custombib from preamble
+        \message{custombib option is chosen}
         \useCustomBibtrue
-        \setBibtrue % Need to evaluate is bibliography is loaded
+        \AtBeginDocument{
+          \@ifpackageloaded{natbib}{true}{
+            \@ifpackageloaded{biblatex}{true}{
+              \ClassWarning{PhDThesisPSnPDF}{%
+                Custom bibliography is chosen, but no corresponding package 
+                (biblatex/natbib) has been loaded. Please load the
+                appropriate bibliography package in the preamble.}
+            }
+          }
+        }
+        \setBibtrue
       \fi
     \else                                     % set default to numbered
+      \message{custombib option is NOT chosen} 
       \ifPHD@biblatex
         \RequirePackage[backend=biber, style=numeric-comp,
           citestyle=numeric, sorting=none, natbib=true]{biblatex}
-        \setBiBLaTeXtrue
+        \setBiBLaTeXfalse
       \else
         \RequirePackage[numbers,sort&compress]{natbib} 
       \fi
-      \setBibtrue
-      \ClassWarning{PhDThesisPSnPDF}{No bibliography style was specified.
-         Default numbered style is used. If you would like to use a 
-         different style, use `authoryear' or `numbered' in the options in
-         documentclass or use `custombib` and define the natbib package or
-         biblatex package with required style in the Preamble.tex file}
+      \setBibfalse
     \fi % custombib
   \fi % numbered
 \fi % author year
 
-
+\ifsetBib
+\else
+\ClassWarning{PhDThesisPSnPDF}{No bibliography style was specified.
+  Default numbered style is used. If you would like to use a 
+  different style, use `authoryear' or `numbered' in the options in
+  documentclass or use `custombib` and define the natbib package or
+  biblatex package with required style in the Preamble.tex file}
+\fi
 
 % *********************** To copy ligatures and Fonts **************************
 \RequirePackage{textcomp}

Preamble/preamble.tex

@@ -5,8 +5,8 @@
 % Set {innerside margin / outerside margin / topmargin / bottom margin}  and
 % other page dimensions
 \ifsetCustomMargin
-   \RequirePackage[left=37mm,right=30mm,top=35mm,bottom=30mm]{geometry}
-   \setFancyHdr % To apply fancy header after geometry package is loaded
+  \RequirePackage[left=37mm,right=30mm,top=35mm,bottom=30mm]{geometry}
+  \setFancyHdr % To apply fancy header after geometry package is loaded
 \fi
 
 % *****************************************************************************
@@ -15,9 +15,9 @@
 % Add `customfont' in the document class option to use this section
 
 \ifsetCustomFont
-    % Set your custom font here and use `customfont' in options. Leave empty to
-    % load computer modern font (default LaTeX font).
-    \RequirePackage{libertine}
+  % Set your custom font here and use `customfont' in options. Leave empty to
+  % load computer modern font (default LaTeX font).
+  \RequirePackage{libertine}
 \fi
 
 % *****************************************************************************
@@ -93,7 +93,7 @@
 
 % Add `custombib' in the document class option to use this section
 \ifuseCustomBib
-   \RequirePackage[square, sort, numbers, authoryear]{natbib} % CustomBib
+   %\RequirePackage[square, sort, numbers, authoryear]{natbib} % CustomBib
 
 % If you would like to use biblatex for your reference management, as opposed to the default `natbibpackage` pass the option `custombib` in the document class. Comment out the previous line to make sure you don't load the natbib package. Uncomment the following lines and specify the location of references.bib file