android: Catch NullPointerException when parsing invalid certificates

src/frontends/android/app/src/main/java/org/strongswan/android/security/TrustedCertificateEntry.java

@@ -43,6 +43,8 @@ public class TrustedCertificateEntry implements Comparable<TrustedCertificateEnt
 		mCert = cert;
 		mAlias = alias;
 
+		try
+		{
 			SslCertificate ssl = new SslCertificate(mCert);
 			String o = ssl.getIssuedTo().getOName();
 			String ou = ssl.getIssuedTo().getUName();
@@ -68,6 +70,13 @@ public class TrustedCertificateEntry implements Comparable<TrustedCertificateEnt
 				mSubjectPrimary = ssl.getIssuedTo().getDName();
 			}
 		}
+		catch (NullPointerException ex)
+		{
+			/* this has been seen in Play Console for certificates for which notBefore apparently
+			 * can't be parsed (which SslCertificate() does) */
+			mSubjectPrimary = cert.getSubjectDN().getName();
+		}
+	}
 
 	/**
 	 * The main subject of this certificate (O, CN or the complete DN, whatever