perf: avoid branch in parser csi param action

src/terminal/Parser.zig

@@ -349,9 +349,7 @@ inline fn doAction(self: *Parser, action: TransitionAction, c: u8) ?Action {
             }
 
             // A numeric value. Add it to our accumulator.
-            if (self.param_acc_idx > 0) {
-                self.param_acc *|= 10;
-            }
+            self.param_acc *|= 10;
             self.param_acc +|= c - '0';
 
             // Increment our accumulator index. If we overflow then