Reset currentRow and currentCol on clear (#1076)

pyqtgraph/graphicsItems/GraphicsLayout.py

@@ -167,6 +167,8 @@ class GraphicsLayout(GraphicsWidget):
     def clear(self):
         for i in list(self.items.keys()):
             self.removeItem(i)
+        self.currentRow = 0
+        self.currentCol = 0
 
     def setContentsMargins(self, *args):
         # Wrap calls to layout. This should happen automatically, but there