Fix component PubMed (#2192)

### What problem does this PR solve?


### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

agent/component/pubmed.py

@@ -49,11 +49,19 @@ class PubMed(ComponentBase, ABC):
             pubmedids = Entrez.read(Entrez.esearch(db='pubmed', retmax=self._param.top_n, term=ans))['IdList']
             pubmedcnt = ET.fromstring(
                 Entrez.efetch(db='pubmed', id=",".join(pubmedids), retmode="xml").read().decode("utf-8"))
-            pubmed_res = [{"content": 'Title:' + child.find("MedlineCitation").find("Article").find(
-                "ArticleTitle").text + '\nUrl:<a href=" https://pubmed.ncbi.nlm.nih.gov/' + child.find(
-                "MedlineCitation").find("PMID").text + '">' + '</a>\n' + 'Abstract:' + child.find(
-                "MedlineCitation").find("Article").find("Abstract").find("AbstractText").text} for child in
-                          pubmedcnt.findall("PubmedArticle")]
+            pubmed_res = []
+            for child in pubmedcnt.findall("PubmedArticle"):
+                if child.find("MedlineCitation").find("Article").find("ArticleTitle").text:
+                    title_tmp = 'Title:' + child.find("MedlineCitation").find("Article").find("ArticleTitle").text
+                else:
+                    title_tmp = 'Title:' + "".join(
+                        [childtitle.text for childtitle in
+                         child.find("MedlineCitation").find("Article").find("ArticleTitle")])
+                url_tmp = '\nUrl:<a href=" https://pubmed.ncbi.nlm.nih.gov/' + child.find("MedlineCitation").find(
+                    "PMID").text + '">' + '</a>'
+                abstract_tmp = '\nAbstract:' + child.find("MedlineCitation").find("Article").find("Abstract").find(
+                    "AbstractText").text
+                pubmed_res.append({"content": title_tmp + url_tmp + abstract_tmp})
         except Exception as e:
             return PubMed.be_output("**ERROR**: " + str(e))