[chronojump] Fixed a possible problem of maximumIsometricForce.R on really small files

[Xavier de Blas <xaviblas src gnome org>]

commit c4d8dfecc525a29a5008f14d4cc92c5c359ca887
Author: Xavier de Blas <xaviblas gmail com>
Date:   Tue Mar 9 22:34:02 2021 +0100

    Fixed a possible problem of maximumIsometricForce.R on really small files

 r-scripts/maximumIsometricForce.R | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/r-scripts/maximumIsometricForce.R b/r-scripts/maximumIsometricForce.R
index 2446a615..2fc21da3 100644
--- a/r-scripts/maximumIsometricForce.R
+++ b/r-scripts/maximumIsometricForce.R
@@ -1127,10 +1127,10 @@ plotABGraph <- function(pngFile, dataFile, decimalChar, title, exercise, datetim
        points(x[which(y == max(y))[1]], max(y), col="red", cex=2)
 
        #draw a segment related to max avg force in window
-       segments(x[maxAvgForceInWindowSampleStart], maxAvgForceInWindow,
-                x[maxAvgForceInWindowSampleEnd], maxAvgForceInWindow, lwd=2, col="green4")
        if(maxAvgForceInWindow > 0)
        {
+               segments(x[maxAvgForceInWindowSampleStart], maxAvgForceInWindow,
+                        x[maxAvgForceInWindowSampleEnd], maxAvgForceInWindow, lwd=2, col="green4")
                topTick = maxAvgForceInWindow/100
                segments(x[maxAvgForceInWindowSampleStart], maxAvgForceInWindow - topTick,
                         x[maxAvgForceInWindowSampleStart], maxAvgForceInWindow + topTick,