Fix RPMLint msg: Returns random data in a function

In mudlet::getMudletPath, I chose to return an empty string,
and in TTextEdit:getSelectedText, I returned whatever happens to
have been added to the buffer before hitting the end of the loop.

Also, Q_UNREACHABLE has been added to throw errors if needed.

src/TTextEdit.cpp

@@ -1390,6 +1390,8 @@ QString TTextEdit::getSelectedText(char newlineChar)
         // we never append the last character of a buffer line se we set our own
         text.append(newlineChar);
     }
+    qDebug() << "TTextEdit::getSelectedText(...) INFO - unexpectedly hit bottom of method so returning:" << text;
+    return text;
 }
 
 void TTextEdit::mouseReleaseEvent(QMouseEvent* event)

src/mudlet.cpp

@@ -3402,6 +3402,8 @@ QString mudlet::getMudletPath(const mudletPathType mode, const QString& extra1,
         // when saving/resyncing packages/modules - ends in a '/'
         return QStringLiteral("%1/.config/mudlet/moduleBackups/").arg(QDir::homePath());
     }
+    Q_UNREACHABLE();
+    return QString();
 }
 
 #if defined(INCLUDE_UPDATER)