don't allow breakpoints to be set on blank lines (fixes #3765)

core/todo.txt

@@ -37,6 +37,8 @@ X line direction vectors are incorrectly transformed
 X   https://github.com/processing/processing/issues/3779
 X Strokes in 3D PShapes are not properly connected
 X   https://github.com/processing/processing/issues/3756
+X setting surface properties hangs OpenGL sketches
+X   https://github.com/processing/processing/issues/3789
 
 jakub
 X FX - fix transformation stack NPE
@@ -110,7 +112,6 @@ _ update wiki/docs to say "don't override sketchXxxx() methods"
 _ SVG only exports last frame
 _   possibly because Java2D is disposing the Graphics2D in between?
 _   https://github.com/processing/processing/issues/3753
-
 _ selectInput/Output() is behind the drawing window (Windows)
 _   https://github.com/processing/processing/issues/3775
 

java/src/processing/mode/java/Debugger.java

@@ -477,10 +477,15 @@ public class Debugger implements VMEventListener {
    */
   synchronized void toggleBreakpoint(int lineIdx) {
     LineID line = editor.getLineIDInCurrentTab(lineIdx);
+    int index = line.lineIdx();
     if (hasBreakpoint(line)) {
-      removeBreakpoint(line.lineIdx());
+      removeBreakpoint(index);
     } else {
-      setBreakpoint(line.lineIdx());
+      // Make sure the line contains actual code before setting the break
+      // https://github.com/processing/processing/issues/3765
+      if (editor.getLineText(index).trim().length() != 0) {
+        setBreakpoint(index);
+      }
     }
   }
 

todo.txt

@@ -17,6 +17,8 @@ X   https://github.com/processing/processing/issues/3786
 X confusion when // tweak is used
 X   https://github.com/processing/processing/issues/3742
 X   change to /// tweak instead
+X don't allow breakpoints to be set on blank lines
+X   https://github.com/processing/processing/issues/3765
 
 jakub
 X Error/warning location visualisation not updating when editor resizes
@@ -67,6 +69,7 @@ _   https://github.com/processing/processing/issues/3543
 _   move to javapackager or another option?
 _   http://www.excelsiorjet.com/kb/35/howto-create-a-single-exe-from-your-java-application
 _ mouse events (i.e. toggle breakpoint) seem to be firing twice
+_ non-standard cursor images used for OpenGL
 
 
 3.0 final
@@ -113,8 +116,6 @@ _ add this to the preferences?
 
 
 gui
-_ don't allow breakpoints to be set on blank lines
-_   https://github.com/processing/processing/issues/3765
 _ different design of squiggly line?
 _ build custom scroll bar since the OS versions are so ugly?
 _ error/warning location is awkward when no scroll bar is in use