Optimize KisToolSelectSimilar for Color Labeled Layers

Before this commit, KisToolSelectSimilar in Color Labeled Layers mode
would use the whole image bounds area to calculate the selection.
This commit ensures that the areas outside of bounds of the source
device are not processed unnecessarily.

CCBUG:428441

plugins/tools/selectiontools/kis_tool_select_similar.cc

@@ -187,7 +187,10 @@ void KisToolSelectSimilar::beginPrimaryAction(KoPointerEvent *event)
                     [fuzziness, tmpSel, sourceDevice, patch, color] () mutable -> KUndo2Command* {
 
                         QRect patchRect = *patch.data();
-                        selectByColor(sourceDevice, tmpSel, color->data(), fuzziness, patchRect);
+                        QRect finalRect = patchRect.intersected(sourceDevice->exactBounds());
+                        if (!finalRect.isEmpty()) {
+                            selectByColor(sourceDevice, tmpSel, color->data(), fuzziness, patchRect);
+                        }
                         return 0;
         });