Fix bug

Fix the bug that occurs when the pdf does'nt have title or author.

app.py

@@ -20,14 +20,20 @@ def summarize_pdf(pdf_file):
     if pdf_file is not None: 
         with st.spinner('Generando resumen, espera un poco...'):
             reader = PyPDF2.PdfReader(pdf_file)
-            title = reader.metadata.title
-            author = reader.metadata.author
+            if reader.metadata.title == None
+                title = ''
+            else:
+                title = reader.metadata.title
+            if reader.metadata.author == None
+                author = ''
+            else:
+                author = reader.metadata.author            
             pages =reader.pages
             text = [pages[i].extract_text() for i in range(len(pages))]
             text = [utils.drop_non_relevant_text(utils.preprocess_text(x)) for x in text]
             text = [' '.join(x) for x in text]
             text=[x+'\n' if len(x) < 50 else generate_summary(x)+'  \n' for x in text]
-            results = [reader.metadata.title+'  \n', reader.metadata.author+'  \n'] + text
+            results = [title+'  \n', author+'  \n'] + text
             st.session_state["summary"] = ' '.join(results)
 
 ## Graphic interfaz