Make sure we clear out the text fields when drawing text in custom rects on the GPU view.

Author: mikepj

Graph Views/XRGGPUView.m

@@ -223,6 +223,10 @@ - (void)drawGraph {
 			}
 		}
 
+        self.leftLabel.stringValue = @"";
+        self.centerLabel.stringValue = @"";
+        self.rightLabel.stringValue = @"";
+        
         [leftText drawInRect:textRect withAttributes:[appSettings alignLeftAttributes]];
         [centerText drawInRect:textRect withAttributes:[appSettings alignCenterAttributes]];
         [rightText drawInRect:textRect withAttributes:[appSettings alignRightAttributes]];