scripted-diff: return error(...); ==> error(...); return false;

This is needed for the next commit.

-BEGIN VERIFY SCRIPT-
 # Separate sed invocations to replace one-line, and two-line error(...) calls
 sed -i             --regexp-extended 's!( +)return (error\(.*\);)!\1\2\n\1return false;!g'             $( git grep -l 'return error(' )
 sed -i --null-data --regexp-extended 's!( +)return (error\([^\n]*\n[^\n]*\);)!\1\2\n\1return false;!g' $( git grep -l 'return error(' )
-END VERIFY SCRIPT-

src/kernel/coinstats.cpp

@@ -134,7 +134,8 @@ static bool ComputeUTXOStats(CCoinsView* view, CCoinsStats& stats, T hash_obj, c
             outputs[key.n] = std::move(coin);
             stats.coins_count++;
         } else {
-            return error("%s: unable to read value", __func__);
+            error("%s: unable to read value", __func__);
+            return false;
         }
         pcursor->Next();
     }