feat: return an error when an invalid scale count is encountered

Closes #5710

plugins/common/common.go

@@ -394,7 +394,10 @@ func ParseScaleOutput(b []byte) (map[string]int, error) {
 	scale := make(map[string]int)
 
 	for _, line := range strings.Split(string(b), "\n") {
-		s := strings.Split(line, "=")
+		s := strings.SplitN(line, "=", 2)
+		if len(s) != 2 {
+			return scale, fmt.Errorf("invalid scale output stored by dokku: %v", line)
+		}
 		processType := s[0]
 		count, err := strconv.Atoi(s[1])
 		if err != nil {