Use a return value instead of just Q_ASSERT - don't crash in production

(cherry picked from commit cb1536aaba)

src/History.cpp

@@ -507,7 +507,11 @@ int CompactHistoryScroll::getLines()
 
 int CompactHistoryScroll::getLineLen(int lineNumber)
 {
-    Q_ASSERT(lineNumber >= 0 && lineNumber < _lines.size());
+    if ((lineNumber < 0) || (lineNumber >= _lines.size())) {
+        kDebug() << "requested line invalid: 0 < " << lineNumber << " < " <<_lines.size();
+        Q_ASSERT(lineNumber >= 0 && lineNumber < _lines.size());
+        return 0;
+    }
     CompactHistoryLine* line = _lines[lineNumber];
     //kDebug() << "request for line at address " << line;
     return line->getLength();

src/tests/HistoryTest.cpp

@@ -126,8 +126,8 @@ void HistoryTest::testHistoryScroll()
     historyScroll = new CompactHistoryScroll(42);
     QVERIFY(historyScroll->hasScroll());
     QCOMPARE(historyScroll->getLines(), 0);
-    // QASSERT catches this - QCOMPARE(historyScroll->getLineLen(0), 0);
-    // QASSERT catches this - QCOMPARE(historyScroll->getLineLen(10), 0);
+    QCOMPARE(historyScroll->getLineLen(0), 0);
+    QCOMPARE(historyScroll->getLineLen(10), 0);
 
     const HistoryType& compactHistoryType = historyScroll->getType();
     QCOMPARE(compactHistoryType.isEnabled(), true);