Fix dimensionless quantities dash display

Encapsulating in 'si' prints fine in text AND math mode

bib/glossaries/symbols/greek.bib

@@ -4,7 +4,7 @@
 @symbol{ratio_of_specific_heats,
     name={\ensuremath{\kappa}},
     description={Ratio of specific heats},
-    unit={--},
+    unit={\si{-}},
 }
 @symbol{celsius_temperature,
     name={\ensuremath{\vartheta}},
@@ -22,7 +22,7 @@ @symbol{relative_humidity
 @symbol{mass_fraction,
     name={\ensuremath{\gamma}},
     description={Mass fraction},
-    unit={--},
+    unit={\si{-}},
 }
 @symbol{angle_one,
     name={\ensuremath{\alpha}},

bib/glossaries/symbols/other.bib

@@ -28,7 +28,7 @@ @entry{flow
 @entry{nabla,
     name={\nablaoperatorfmt{\symbolplaceholder}},
     description={Vector of partial derivatives (Nabla operator) of \symbolplaceholder},
-    unit={--},
+    unit={\si{-}},
 }
 @entry{mean,
     name={\meanfmt{\symbolplaceholder}},
@@ -43,7 +43,7 @@ @entry{logmean
 @entry{vector,
     name={\ensuremath{\vectfmt{x}}},
     description={Vector},
-    unit={--},
+    unit={\si{-}},
 }
 @entry{abs,
     name={\ensuremath{\absfmt*{\symbolplaceholder}}},

bib/glossaries/symbols/roman.bib

@@ -137,18 +137,18 @@ @symbol{electrical_resistance
 @symbol{mach_number,
     name={\ensuremath{\operatorname{M}}},
     description={\glsfmtname{name.ernst_mach} number},
-    unit={--},
+    unit={\si{-}},
 }
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 % Other
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 @symbol{component,
     name={\ensuremath{n}},
     description={Component},
-    unit={--},
+    unit={\si{-}},
 }
 @symbol{count,
     name={\ensuremath{k}},
     description={Count/Quantity},
-    unit={--},
+    unit={\si{-}},
 }