Ignore disabled monitors for -m

Don't check monitors without dimensions in xrandr's output.
Addresses #26.

tdrop

@@ -244,16 +244,18 @@ update_geometry_settings_for_monitor() {
 		monitors_info=$(xrandr --query | awk '/ connected/ {gsub("primary ",""); print}')
 		while read -r monitor; do
 			monitor_geo=$(echo "$monitor" | awk '{print $3}')
-			x_begin=$(echo "$monitor_geo" | awk -F '+' '{print $2}')
+			if [[ $monitor_geo =~ ^[0-9]+x[0-9]+\+[0-9]+\+[0-9]+$ ]]; then
-			y_begin=$(echo "$monitor_geo" | awk -F '+' '{print $3}')
+				x_begin=$(echo "$monitor_geo" | awk -F '+' '{print $2}')
-			x_width=$(echo "$monitor_geo" | awk -F 'x' '{print $1}')
+				y_begin=$(echo "$monitor_geo" | awk -F '+' '{print $3}')
-			y_height=$(echo "$monitor_geo" | awk -F 'x|+' '{print $2}')
+				x_width=$(echo "$monitor_geo" | awk -F 'x' '{print $1}')
-			x_end=$((x_begin+x_width))
+				y_height=$(echo "$monitor_geo" | awk -F 'x|+' '{print $2}')
-			y_end=$((y_begin+y_height))
+				x_end=$((x_begin+x_width))
-			if [[ $window_x -ge $x_begin ]] && [[ $window_x -lt $x_end ]] && \
+				y_end=$((y_begin+y_height))
-				[[ $window_y -ge $y_begin ]] && [[ $window_y -lt $y_end ]]; then
+				if [[ $window_x -ge $x_begin ]] && [[ $window_x -lt $x_end ]] && \
-				current_monitor=$(echo "$monitor" | awk '{print $1}')
+					[[ $window_y -ge $y_begin ]] && [[ $window_y -lt $y_end ]]; then
-				break
+					current_monitor=$(echo "$monitor" | awk '{print $1}')
+					break
+				fi
 			fi
 		done <<< "$monitors_info"
 	fi