Do not draw if the datasource width is negative. Tries to work around a crash...

Do not draw if the datasource width is negative. Tries to work around a crash pending the root cause's discovery.

sources/PTYTextView.m

@@ -1077,6 +1077,10 @@ static const int kDragThreshold = 3;
 }
 - (void)drawRect:(NSRect)rect {
+    if (_dataSource.width <= 0) {
+        ITCriticalError(_dataSource.width < 0, @"Negative datasource width of %@", @(_dataSource.width));
+        return;
+    }
     BOOL savedCursorVisible = _drawingHelper.cursorVisible;
     // Try to use a saved grid if one is available. If it succeeds, that implies that the cursor was