[processing][grass] Fix broken r.cost algorithm

Author: nyalldawson

python/plugins/processing/algs/grass7/description/r.cost.txt

@@ -2,8 +2,8 @@ r.cost
 Creates a raster layer of cumulative cost of moving across a raster layer whose cell values represent cost.
 Raster (r.*)
 QgsProcessingParameterRasterLayer|input|Unit cost layer|None|False
-QgsProcessingParameterPoint|start_coordinates|Coordinates of starting point(s) (E,N)|0,0|False
-QgsProcessingParameterPoint|stop_coordinates|Coordinates of stopping point(s) (E,N)|0,0|False
+QgsProcessingParameterPoint|start_coordinates|Coordinates of starting point(s) (E,N)||True
+QgsProcessingParameterPoint|stop_coordinates|Coordinates of stopping point(s) (E,N)||True
 QgsProcessingParameterBoolean|-k|Use the 'Knight's move'; slower, but more accurate|False
 QgsProcessingParameterBoolean|-n|Keep null values in output raster layer|True
 QgsProcessingParameterFeatureSource|start_points|Start points|0|None|True
@@ -12,6 +12,6 @@ QgsProcessingParameterRasterLayer|start_raster|Name of starting raster points ma
 QgsProcessingParameterNumber|max_cost|Maximum cumulative cost|QgsProcessingParameterNumber.Double|0.0|True|None|None
 QgsProcessingParameterNumber|null_cost|Cost assigned to null cells. By default, null cells are excluded|QgsProcessingParameterNumber.Double|None|True|None|None
 QgsProcessingParameterNumber|memory|Maximum memory to be used in MB|QgsProcessingParameterNumber.Integer|300|True|1|None
-QgsProcessingParameterRasterDestination|output|Cumulative cost
-QgsProcessingParameterRasterDestination|nearest|Cost allocation map
-QgsProcessingParameterRasterDestination|outdir|Movement directions
+QgsProcessingParameterRasterDestination|output|Cumulative cost|None|True
+QgsProcessingParameterRasterDestination|nearest|Cost allocation map|None|True
+QgsProcessingParameterRasterDestination|outdir|Movement directions|None|True