[processing] Fix IDW parameter value creation

nyalldawson · nyalldawson · commit 1e662d1e7ca6 · 2019-03-14T08:18:44.000+10:00
diff --git a/python/plugins/processing/algs/qgis/ui/InterpolationWidgets.py b/python/plugins/processing/algs/qgis/ui/InterpolationWidgets.py
@@ -201,11 +201,11 @@ def value(self):
                 else:
                     inputType = QgsInterpolator.SourceBreakLines
 
-            layers += '{}::~::{:d}::~::{:d}::~::{:d}::|::'.format(layer.source(),
-                                                                  interpolationSource,
-                                                                  fieldIndex,
-                                                                  inputType)
-        return layers[:-1]
+                layers += '{}::~::{:d}::~::{:d}::~::{:d}::|::'.format(layer.source(),
+                                                                      interpolationSource,
+                                                                      fieldIndex,
+                                                                      inputType)
+        return layers[:-len('::|::')]
 
 
 class InterpolationDataWidgetWrapper(WidgetWrapper):
